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Synthesis of novel mononuclear and dinuclear ruthenium(II) complexes with terpyridine and acetylacetonate ancillary ligands and cyanamide derivative ligands
Inorganica Chimica Acta 358 (2005) 2384–2394 www.elsevier.com/locate/ica
Synthesis of novel mononuclear and dinuclear ruthenium(II) complexes with terpyridine and acetylacetonate ancillary ligands and cyanamide derivative ligands Muriel A. Fabre, Joe¨l Jaud, Jacques J. Bonvoisin
*
CEMES/CNRS – NanoSciences Group, 29 rue Jeanne Marvig, BP 94347, 31055 Toulouse Cedex 4, France Received 9 December 2004; accepted 11 January 2005 Available online 7 February 2005
Abstract Several new mononuclear and dinuclear ruthenium(II) complexes – incorporating 2,2 0 :6 0 ,200 -terpyridine and acetylacetonate as ancillary ligands and phenylcyanamide derivative ligands – of the type [Ru(tpy)(acac)(L)] and [{Ru(tpy)(acac)}2(l-L 0 )] (where tpy = 2,2 0 :6 0 ,200 -terpyridine, acac = acetylacetonate, L = hmbpcyd = 4-(3-hydroxy-3-methylbutynyl)phenylcyanamide anion (2) and epcyd = 4-ethynylphenylcyanamide anion (3) and L 0 = bcpda = bis(4-cyanamidophenyl)diacetylene dianion (4) and bcpea = 9,10bis(4-cyanamidophenylethynyl)anthracene dianion (5)) were synthesized in a stepwise manner starting from [Ru(tpy)(acac)(Ipcyd)] (1), where Ipcyd = 4-iodophenylcyanamide anion. Tetraphenylarsonium salts of the phenylcyanamide derivative ligands were also prepared. The four complexes have been characterized by UV–Vis, IR, ES-MS, electrochemistry and 1H NMR. Mononuclear complexes 2 and 3 were further characterized by 13C NMR. The single crystal X-ray structure of 2 was determined, it crystallized with one molecule of water with empirical formula of C32H31N5O5Ru, in a monoclinic crystal system and space group of P21/n with ˚ , b = 9.634(2) A ˚ , c = 20.063(7) A ˚ , b = 92.65(3), V = 3406(2) A ˚ 3 and Z = 4. The structure was refined to a final R faca = 17.642(5) A tor of 0.040. The Ru(III/II) couple of 1–3 appeared around 0.34 V versus the saturated calomel electrode in dimethylformamide and at a slightly higher potential, around 0.36–0.37 V for 4 and 5. Spectroelectrochemical studies were also performed for 4 and 5, no intervalence transition was observed despite all attempts. 2005 Elsevier B.V. All rights reserved. Keywords: Molecular electronics; Mononuclear and dinuclear ruthenium(II) complexes; Cyanamide derivatives; X-ray structure; Spectroelectrochemical studies
1. Introduction In the molecular electronics field, it is important to evaluate the capacity of a molecule to conduct electrons. A possible way is to synthesize bimetallic complexes where the molecule to test is a bridging ligand or a spacer between two metallic sites [1,2]. The electronic communication between two metallic centers through a bridging ligand can then be assessed by the electronic *
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99. E-mail address: [email protected] (J.J. Bonvoisin). 0020-1693/$ - see front matter 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2005.01.004
coupling parameter Vab in the mixed valence form [3]. However, the method, which consists of measuring the parameter Vab by UV–Vis near IR spectroscopy through the intervalence transition [4], has experimental limits. ˚ For long molecules (with a distance greater than 25 A between the two redox centers), the intervalence transition becomes almost undetectable. An alternative could be to measure the magnetic coupling parameter J between the two metallic centers through the bridging ligand in the paramagnetic homovalent form of the dinuclear complex [5–7]. This parameter can be given by magnetic susceptibility or EPR techniques. The correlation between the two parameters Vab and J has still
M.A. Fabre et al. / Inorganica Chimica Acta 358 (2005) 2384–2394
to be settled. First, good candidates have to be found, where the interactions are strong enough to be measurable in both forms (mixed-valence and paramagnetic homovalent) of the dinuclear complexes. Crutchley [5] showed that cyanamide (NCN) groups included in a bridging ligand were particularly well suited to promote such strong interactions between two metallic sites either in homovalent [8] or mixed-valence [9,10] ruthenium complexes. Recent theoretical studies performed by Ruiz and coworkers corroborate this point and conclude that dicyd-type bridging ligands constitute interesting goals for obtaining strong exchange coupling of paramagnetic ions at very long distance [11]. Previous work showed that dinuclear ruthenium complexes with a phenylcyanamide derivative as bridging ligand and terpyridine, bipyridine as ancillary ligands are not suitable for this purpose, the bridging ligand being oxidized before the ruthenium(II) atoms [7,12] due presumably to the acceptor character of the bipyridine ligand. This led us to replace the bipyridine ligand by a donor group such as acetylacetonate, which has shown its capacity to tune the redox potential of ruthenium complexes [13]. Following this line, we succeeded to synthesize a neutral building block [Ru(tpy)(acac)(Ipcyd)] (where Ipcyd = 4-iodophenylcyanamide) and incidentally a ruthenium complex containing a zwitterionic form of the phosphoniophenylcyanamide ligand [14]. Here, we present the successful synthesis of four new ruthenium complexes starting from [Ru(tpy)(acac)(Ipcyd)] (1): two mononuclear complexes, [Ru(tpy)(acac)(L)], where L = hmbpcyd = 4-(3hydroxy-3-methylbutynyl)phenylcyanamide anion (2) and epcyd = 4-ethynylphenylcyanamide anion (3), and two dinuclear complexes, [{Ru(tpy)(acac)}2(l-L 0 )], where L 0 = bcpda = bis(4-cyanamidophenyl)diacetylene dianion (4) and bcpea = 9,10-bis(4-cyanamidophenylethynyl)anthracene dianion (5). Optical and electrochemical properties of 1–5 are reported and compared. The spectroelectrochemical properties of complexes 4 and 5 are also reported. The free phenylcyanamide derivative ligands in their deprotonated form (tetraphenylarsonium salts) are also presented here for the sake of a better understanding of the spectroscopic and electrochemical properties of the corresponding complexes.
2. Results and discussion 2.1. Synthesis The synthesis of [Ru(tpy)(acac)(epcyd)] (3) from [Ru(tpy)(acac)(Ipcyd)] (1) in two steps via [Ru(tpy)(acac)(hmbpcyd)] (2) was adapted from literature procedures [15]. The carbinol-protected alkyne complex [Ru(tpy)(acac)(hmbpcyd)] (2) was prepared by a Sono-
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gashira cross-coupling reaction between the iodoruthenium complex [Ru(tpy)(acac)(Ipcyd)] (1) and 2methylbut-3-yn-2-ol under classic conditions (Pd(PPh3)4, CuI, piperidine, and DMF). The ethynylated complex [Ru(tpy)(acac)(epcyd)] (3) could then be obtained by a deprotection reaction of [Ru(tpy)(acac)(hmbpcyd)] (2) by tBuOK in DMF. [Ru(tpy)(acac)(epcyd)] (3) was then used as a synthon in a homo-coupling reaction to form the diyne dinuclear complex [{Ru(tpy)(acac)}2(l-bcpda)] (4). This reaction was performed using DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) and copper(I) chloride in dry pyridine with oxygen bubbling [16]. A general scheme is shown in Scheme 1. Complex [{Ru(tpy)(acac)}2(l-bcpea)] (5) was synthesized by a Sonogashira cross-coupling reaction between the iodoruthenium complex [Ru(tpy)(acac)(Ipcyd)] (1) and 9,10-diethynylanthracene under classic conditions (Scheme 2). It has to be noted that complexes 4 and 5 are poorly soluble in every solvent. The best solubility was found with DMF, which is why all spectroscopic and electrochemical studies were performed in this solvent. The free phenylcyanamide derivative ligands were also synthesized in order to have a better understanding of the physico-chemical properties of the complexes. First, the ligands were prepared in their neutral protonated form from IpcydH, using the same coupling reaction conditions as for the complexes (Scheme 3). The tetraphenylarsonium salts of the anionic deprotonated ligands were then obtained according to a general procedure [8]. 2.2. Electrochemical studies Cyclic voltammograms of the tetraphenylarsonium salts of the anionic ligands and of the complexes were recorded in dimethylformamide under an argon atmosphere with 0.1 M tetrabutylammonium hexafluorophosphate (TBAH). Cyclic voltammetry data for the investigated species are given in Table 1. The E1/2 potentials were determined from the average of the anodic and cathodic peak potentials for reversible waves. For irreversible waves, the anodic peak potentials are reported. The voltammograms of the tetraphenylarsonium salts of the free anionic ligands present an irreversible wave in oxidation around 0.5 V. The three mononuclear complexes (1, 2 and 3) present very similar voltammetric behaviors. The voltammograms show two waves in oxidation (Fig. 1). The first wave at 0.34 V was attributed to the Ru(II/III) couple. As shown in the inset of Fig. 1, this wave became quasi-reversible when scan range was decreased to 0.8 V, with peak to peak separation of 78 mV independent of scan rate from 0.1 to 1.0 V/s. The second wave around 1.1 V is irreversible. It is very probably due to the
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M.A. Fabre et al. / Inorganica Chimica Acta 358 (2005) 2384–2394 N N N
I
N
Ru
N
2-methylbut-3-yn-2-ol N
O DMF/piperidine
O
N
OH
Pd(PPh3)4/CuI
N
N Ru
O O
N
2 77%
1
tBuOK DMF N
O O
Ru N N
N N N
N N
N DBU CuCl, O2
N Ru
O pyridine
O
N
N N
H
N Ru
O O
N
4
3
35%
60%
Scheme 1. General scheme for the synthesis of complexes 2, 3 and 4.
O O
H N N N
H N
N Ru
O O
N
CuI, Pd(PPh3)4 DMF/piperidine
Ru N N
I
N N
N
N
N Ru
N
N
O O
5 1
35%
Scheme 2. Synthesis of [{Ru(tpy)(acac)}2(l-bcpea)] (5).
irreversible oxidation of the phenylcyanamide anionic ligand as it was demonstrated in a previous study on [Ru(tpy)(bpy)(Ipcyd)] [12]. It is also confirmed by the study of the tetraphenylarsonium salts of the ligands. The ligands being stabilized when coordinated to the Ruthenium (III) center, their oxidation shifts anodically (1.1 V versus 0.5 V). In reduction, a quasi-reversible wave around 1.58 V was observed and assigned to the reduction of the terpyridine ligand (see Supporting Information Figure S2 and S3). The voltammograms of the two dinuclear complexes 4 and 5 are quite the same but the Ru(II/III) couple appears at a slightly higher potential (0.36–0.37 V) than the mononuclear complexes 1, 2 and 3 (0.34 V). The anodic shift observed for dinuclear complexes is proba-
bly due to a better conjugation of the bridging ligand decreasing its donor properties and leaving the ruthenium center harder to oxidize. Only one quasi-reversible Ru(II/III) couple is seen, due to the weak coupling between the metal ions and the resultant superimposition of the two one-electron Ru(II/III) couples. At this point, it has to be noted that a single electrochemical wave observed for both dinuclear complexes 4 and 5 does not mean that mixed-valence species are not present in solution [1,17]. Even, in very large systems, where the distance between the metallic sites reaches nanometer size, the comproportionation constant (Kc) tends toward a statistical limit of 4 and at half oxidation, the proportion of mixed-valence species reaches a comfortable 50%.
M.A. Fabre et al. / Inorganica Chimica Acta 358 (2005) 2384–2394 H H
OH
Pd(PPh3)4/CuI N
H
I
tBuOK
H
N OH
DMF/piperidine
N
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DMF
N
IpcydH
N
N
epcydH
hmbpcydH 60%
H
H
69%
H
DBU CuCl, O2 pyridine
Pd(PPh3)4/CuI
DMF/piperidine N
N H
N
N
H N
H
N H
N
N
bcpdaH2 18%
bcpeaH2 71%
Scheme 3. Synthesis of the free phenylcyanamide derivative ligands.
Table 1 Electrochemical data, versus SCE, in DMF, 0.1 M TBAH, 0.1 V/s Species
Oxidation Ru
[As(Ph)4][Ipcyd] [As(Ph)4][hmbpcyd] [As(Ph)4][epcyd] [As(Ph)4]2[bcpda] [As(Ph)4]2[bcpea] 1 2 3 4 5
II/III
, E1/2, V (DE, mV)
– – – – – 0.337 (78) 0.337 (78) 0.342 (78) 0.373 (83) 0.355(83)
Ligand, Ea (V) 0.503 0.483 0.527 0.488 0.474 1.141 1.138 1.162 1.150 1.001
Reduction tpy, E1/2, V (DE, mV) – – – – – 1.588 1.574 1.579 1.569 1.595
(78) (73) (73) (74) (93)
E1/2 = (Ea + Ec)/2; dE = jEa Ecj; Ea: anodic peak potential; Ep: cathodic peak potential.
2.3. Electronic absorption 1.20E-06 5.00E-07
i (A)
9.00E-07
1.00E-07
6.00E-07
-3.00E-07 0
0.2
0.4
0.6
0.8
3.00E-07
0.00E+00
-3.00E-07 0
0.2
0.4
0.6
0.8
1
1.2
1.4
E (V/sce) Fig. 1. Cyclic voltammogram of complex 2, platinum disk working electrode, 0.1 M TBAH in DMF, scan rate 0.1 V/s [scan range: 0 ! +1.5 ! 0 V]; Insert: Cyclic voltammogram of complex 2 [scan range: 0 ! +0.8 ! 0 V].
Electronic absorption data of the tetraphenylarsonium salts of the free ligands and of the complexes have been placed in Table 2. The spectra of the free ligands have been placed in the Supporting Information, Figure S4. The monocyanamide ligands mainly present an intense absorption band around 300 nm, which is attributable to p ! p* transitions. The intensity of this band is almost identical for the three monocyanamide ligands Ipcyd, hmbpcyd, and epcyd (34–37 · 103 M1 cm1) but it has to be noticed that it shifts toward higher wavelengths when the p system of the ligand is increased (292 nm for [As(Ph)4][Ipcyd] versus 320 and 324 nm for [As(Ph)4][hmbpcyd] and [As(Ph)4][epcyd], respectively). The spectrum of biscyanamide ligand [bcpda]2 shows two bands at 377 and 408 nm. The spectrum of biscyanamide ligand [bcpea]2 shows two bands in the UV region (296 and 344 nm) and a broader and more intense band at 560 nm.
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Table 2 UV–Vis absorption data of the investigated compounds Species
Absorption bands,a k in nm (e · 103 in M1 cm1)
[As(Ph)4][Ipcyd] [As(Ph)4][hmbpcyd] [As(Ph)4][epcyd] [As(Ph)4]2[bcpda] [As(Ph)4]2[bcpea] 1
292 (34), 326sh (4.4) 320 (37) 324 (34) 377 (74), 408 (64) 296 (36), 344 (39), 560 (58) 278 (26), 317 (25), 372sh (9.0), 564 (4.9), 607 (4.6) 275 (45), 320 (52), 390sh (12), 568 (5.9), 631 (5.4) 274 (44), 320 (49), 390sh(14), 564 (6.1), 608 (5.7) 277 (63), 319 (62), 399 (66) 408 (66), 564 (10), 630 (9.2) 275 (61), 323 (61), 372sh (39), 492 (9.3), 940sh (17), 1086 (20) 320 (63), 438 (20), 556 (44) 318 (53), 491 (42), 862 (11), 1140 (14)
2 3 4 42+ 5 52+ a
In DMF.
The spectra of complexes 1, 2, 3 and 4 in dimethylformamide (Fig. 2) showed two broad bands in the visible region, which can be assigned to dp(Ru(II)) ! p*(tpy) MLCT transitions [12,14]. This hypothesis is confirmed by the fact that their intensities are almost constant in the three mononuclear complexes and nearly twice the same in the dinuclear complex 4. The two intense bands (around 280 and 320 nm) are attributable to the terpyridine ligand (p ! p* transitions), probably with a superposition of p ! p* transitions of the ligand L in the case of mononuclear complexes 2 and 3, all the more so, since the free deprotonated ligands L of these two complexes show a band in this region. The band that lies between 372 and 390 nm is more controversial. The spectrum of the dinuclear complex 4 shows an additional double band around 400 nm, which we tentatively assign to p ! p* transitions of the bridging ligand L 0 , since the free deprotonated ligand presents two bands
in this region (see also Figure S5 in the Supporting Information). The spectrum of the dinuclear complex 5 also shows two intense bands corresponding to the p ! p* transitions of the terpyridine ligand and one broad and quite intense band at 556 nm, which could be attributed to a superposition of (dp(Ru(II)) ! ptpy) MLCT transitions and intraligand transitions of the bridging ligand L 0 (see also Figure S6 in the Supporting Information). 2.4. Spectroelectrochemistry Spectroelectrochemical studies of the [II,II] dinuclear complex 5 were performed in dimethylformamide to generate [II,III] and [III,III] spectra and are shown in Fig. 3, while the spectra resulting from the stepwise oxidation of dinuclear complex 4 have been placed in the Supporting Information (Figure S7). During the electrochemical oxidation of dinuclear complex 4, the two broad bands at 564 and 630 nm (dp(Ru(II)) ! p*(tpy) MLCT transitions) decrease and one broad band, which can be attributed to a p(L 0 ) ! dp (Ru(III)) LMCT transition, appears at 1086 nm. During the oxidation of complex 5, the bands at 438 and 556 nm decrease and disappear completely, while three bands appear at 491, 862 and 1140 nm. The two broad bands at 862 and 1140 nm can be assigned to the Ru(III)-cyanamide LMCT chromophore. The sharp band at 491 nm could probably be attributed to ILCT. Further studies were performed to try to find a potential intervalence MMCT transition but no additional band could be detected upon oxidation of the dinuclear complexes 4 and 5. These transitions should exist but are probably very weak due to the great distance between the two rutheniums, respectively, 21.7 ˚ (calculated distances) and/or masked by and 25.7 A LMCT transitions. This lack of intervalence transition was not expected, and more specifically for complex 5 because the anthracene unit is supposed to play a special role in mediating electronic effect [18–22] and claimed to be a metal-to-metal communication amplifier when inserted into acetylene linkers [23]. 5
ε/104 (M-1.cm-1)
4 3 2 1 0 350
600
850
1100
1350
1600
1850
λ (nm)
Fig. 2. UV–Vis Spectra of complexes 1, 2, 3, 4 and 5 in DMF.
Fig. 3. Stepwise spectroelectrochemical oxidation of 5 in 0.1 M TBAH in DMF (electrolysis at 0.75 V vs. SCE).
M.A. Fabre et al. / Inorganica Chimica Acta 358 (2005) 2384–2394 Table 3 Crystallographic data and refinement parameters for 2 Formula Crystal system Formula weight (g mol1) Space group ˚) a (A ˚) b (A ˚) c (A b () ˚ 3) V (A Z l (Mo Ka) (mm1) qcalc (g cm3) 2hmax () Total number of reflections Number of unique reflections with I > 3r(I) Absorption correction Tmin/max Rfa Rwb Goodness-of-fit P P a Rf = iFoj jFci/ jFo j. 1=2 P P b Rw ¼ ð wjF o j jF c jÞ2 = wjF o j2 :
C32H29N5O3Ru, H2O monoclinic 650.7 P21/n 17.642(5) 9.634(2) 20.063(7) 92.65(3) 3406(2) 4 0.5 1.269 64 6847 1526 multi-scan 0.538/1.261 0.040 0.113 1.087
2.5. X-ray structure Crystal structure data for [Ru(tpy)(acac)(hmbpcyd)] Æ H2O (2) and selected bond lengths and angles are, respectively, given in Tables 3 and 4. Fig. 4 shows the ORTEP [24] drawing of 2 and the numbering scheme
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Table 4 ˚ ) and bond angles () for 2 Selected bond lengths (A Bond lengths Ru(1)–O(1) Ru(1)–N(1) Ru(1)–N(3) N(4)–C(21) N(5)–C(22) Bond angles O(1)–Ru(1)–O(2) O(1)–Ru(1)–N(2) O(1)–Ru(1)–N(4) O(2)–Ru(1)–N(2) O(2)–Ru(1)–N(4) N(1)–Ru(1)–N(3) N(2)–Ru(1)–N(3) N(3)–Ru(1)–N(4) Ru(1)–O(2)–N(2) N(4)–C(21)–N(5)
2.107(5) 2.077(6) 2.081(7) 1.115(9) 1.416(9) 91.4(2) 176.3(3) 87.4(2) 91.2(2) 177.1(2) 159.9(3) 79.6(3) 86.3(2) 42.7(2) 176.2(9)
Ru(1)–O(2) Ru(1)–N(2) Ru(1)–N(4) N(5)–C(21) C(28)–C(29) O(1)–Ru(1)–N(1) O(1)–Ru(1)–N(3) O(2)–Ru(1)–N(1) O(2)–Ru(1)–N(3) N(1)–Ru(1)–N(2) N(1)–Ru(1)–N(4) N(2)–Ru(1)–N(4) Ru(1)–O(2)–N(1) Ru(1)–N(4)–C(21) C(21)–N(5)–C(22)
2.059(5) 1.939(6) 2.060(6) 1.332(10) 1.188(11) 97.1(3) 103.0(3) 87.5(2) 91.4(2) 80.4(3) 95.3(2) 90.2(2) 46.5(2) 163.6(6) 114.2(6)
used in Table 4. It has to be noticed that the angle between the cyanamide group and the ruthenium atom, i.e., Ru(1)–N(4)–C(21), is 163.6(6), a value which is close to the one obtained for the dinuclear Ru(II) complex [{Ru(tpy)(bpy)}2(l-adpc)]2+ (164.4(2)) [9]. This is in contrast with the value obtained for [Ru(tpy)(bpy)(Ipcyd)]+ [12] (174.5(3)) as well as the ones obtained in the four known crystal structures of Ru(III)-cyanamide complexes [8,25–27], which show an average Ru(III)cyanamide bond angle of 174.6. This has been
Fig. 4. ORTEP drawing of complex [Ru(tpy)(acac)(hmpcyd)] Æ H2O (2) along with the atom numbering scheme (probability level of 30%).
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tentatively explained by a less good p bonding between the ruthenium (II) ion and the cyanamide group, which favors in that case a more bent structure [28]. This may also explain the sharper angle between the cyanamide group and the phenyl group for complex 2, i.e., C(21)– N(5)–C(22) = 114.2(6) compared to the one observed for [Ru(tpy)(bpy)(Ipcyd)]+, which is 120.4(4). One other point to be noticed is that the distance between N(4) and C(21) is the smallest one observed ˚ ), on all the above cited crystal structures (1.115(9) A and suggests a great deal of triple-bond character.
3. Conclusion The present paper illustrates the potentiality of the building block [Ru(tpy)(acac)(Ipcyd)] (1) to give novel mononuclear (2, 3) and dinuclear (4, 5) ruthenium complexes containing cyanamide derivatives. It also shows that the acetylacetonate ligand is definitively well suited to give access to the Ru(III) oxidation state. Spectroelectrochemical studies on dinuclear complexes 4 and 5 did not give the expected results: no intervalence transition in the mixed-valence state could be clearly observed, not even in the presence of a metal-to-metal amplifier unit like the anthracene group. This could be due to the weakness of the IT (given the large inter˚ ) and/or to metallic distance, which is greater than 20 A its being hidden by LMCT transitions. What remains to be done in the near future is to explore the magnetic properties of the now accessible Ru(III)–Ru(III) state of complexes 4 and 5.
4. Experimental 4.1. Materials All chemicals and solvents were of reagent grade or better. IpcydH [12], [Ru(tpy)(acac)(Ipcyd)] [14], tetrakis(triphenylphosphine)palladium(0) [29], 9,10bis(3-hydroxy-3-methylbutynyl)anthracene [18,30] and 9,10-bis[(trimethylsilyl)ethynyl]anthracene [31,32] were prepared according to the literature procedures. Weakly acidic Brockmann I type alumina (Aldrich) and Silica gel 60 (Fluka) were used. 4.2. Physical measurements UV–Vis spectra were recorded on a Shimadzu UV3100 spectrophotometer. 1H NMR spectra were recorded on a Bruker WF-250 spectrometer in CD2Cl2, d6-DMSO, d6-acetone and 13C NMR spectra on a Bruker AMX-500 in d6-DMSO. IR spectra of samples in KBr pellets were taken on a Perkin-Elmer 1725 FT-IR spectrophotometer. Mass spectra were recorded by the
Service de Spectroscopie de Masse of Universite´ Paul Sabatier using FAB (NBA matrix), DCI, EI (Nermag R10-R10) or ES in positive mode (Perkin-Elmer Sciex System API 365). Cyclic voltammograms were obtained with an Autolab system (PGSTAT 100) in dry dimethylformamide (0.1 M tetrabutylammonium hexafluorophosphate, TBAH) at 25 C with a three-electrode system consisting of platinum-disk working (1 mm diameter), platinum-wire counter and saturated calomel reference electrodes. Electrochemical oxidation for complexes 4 and 5 was performed by electrolysis with coulometry in dry dimethylformamide (DMF) (0.1 M TBAH) at 25 C at fixed potential (0.75 V vs SCE) with a three-electrode system consisting of platinum-net working, platinum-wire counter and saturated calomel reference electrodes [33]. 4.3. Synthesis of complexes 4.3.1. Synthesis of [Ru(tpy)(acac)(hmbpcyd)] (2) To a solution of [Ru(tpy)(acac)(Ipcyd)] (1) (170 mg, 0.256 mmol), Pd(PPh3)4 (20 mg, 7 mol%) and CuI (9 mg, 18 mol%) in the previously degassed DMF/piperidine cosolvent (3:1, 4 ml) was added 2-methylbut-3-yn2-ol (0.3 ml, 12 equivalents) under argon and the mixture was reacted for 2 h at room temperature. The solution was then evaporated to dryness. The resulting solid was dissolved in dichloromethane and was purified by column chromatography (weakly acidic alumina, solvent: dichloromethane, eluent: dichloromethane/ethanol 99:1 then 98:2). The second band (dark blue) was collected and then evaporated to dryness to give a dark blue powder of 2 (124 mg, 77%). 1H NMR (see Supporting Information, Figure S1 and Table S1) (CD2Cl2 d = 5.35): 8.73 (2H, ddd, 5.5, 1.5 and 0.8 Hz), 8.19 (2H, ddd, 8.1, 1.5 and 0.8 Hz), 8.11 (2H, d, 8.0 Hz), 7.92 (2H, ddd, 8.1, 7.6 and 1.5 Hz), 7.59 (1H, t, 8.0 Hz), 7.56 (2H, ddd, 7.6, 5.5 and 1.5 Hz), 6.87 (2H, d, 8.6 Hz), 6.02 (2H, d, 8.6 Hz), 5.38 (1H, s), 2.52 (3H, s), 1.55 (6H, s), 1.37 (3H, s). 1H NMR (d6-DMSO d = 2.50): 8.58–8.64 (4H, m), 8.55 (2H, d, 8.1 Hz), 8.07 (2H, ddd, 8.1, 7.5 and 1.4 Hz), 7.74 (1H, t, 8.1 Hz), 7.70 (2H, ddd, 7.5, 5.8 and 1.1 Hz), 6.74 (2H, d, 8.6 Hz), 5.82 (2H, d, 8.6 Hz), 5.33 (1H, s), 5.24 (1H, s), 2.40 (3H, s), 1.39 (6H, s), 1.27 (3H, s).13C NMR (d6-DMSO d = 39.52): 186.2, 185.6, 160.8, 159.4, 153.4, 150.8, 136.4, 131.7, 128.6, 127.0, 125.7, 122.7, 121.4, 118.5, 109.6, 98.9, 93.2, 81.6, 63.7, 32.0, 28.1, 26.8. IR m/cm1 2176s (NCN). ES mass spectrum (CH3CN) m/z: 634 [M + H]+. Anal. Calc. for C32H29N5O3Ru(H2O)1,5: C, 58.3; H, 4.9; N, 10.6. Found: C, 58.0; H, 4.7; N, 10.4%. 4.3.2. Synthesis of [Ru(tpy)(acac)(epcyd)] (3) To a solution of [Ru(tpy)(acac)(hmbpcyd)] (220 mg, 0.348 mmol) in dimethylformamide (9 ml) previously de-
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gassed was added potassium tert-butoxide (44 mg, 0.39 mmol, 1.1 equiv.) under argon. The mixture was heated at 70 C for 1 h and then evaporated to dryness. The dark blue residue was dissolved in 100 ml dichloromethane and washed with water (3 · 30 ml). The organic layer was dried on MgSO4 and evaporated to dryness. The resulting solid was purified by column chromatography (weakly acidic alumina, solvent: dichloromethane, eluent: dichloromethane/ethanol 99:1). The first band (dark blue) was collected, evaporated to dryness and recrystallized from a mixture of dichloromethane and hexane to give a dark blue microcrystalline powder of 3 (120 mg, 60%). 1H NMR (see Supporting Information, Table S2) (CD2Cl2 d = 5.35): 8.73 (2H, ddd, 5.5, 1.6 and 0.8 Hz), 8.17 (2H, ddd, 8.1, 1.4 and 0.8 Hz), 8.08 (2H, d, 8.0 Hz), 7.90 (2H, ddd, 8.1, 7.5 and 1.6 Hz), 7.57 (1H, t, 8.0 Hz), 7.55 (2H, ddd, 7.5, 5.5 and 1.4 Hz), 6.95 (2H, d, 8.7 Hz), 6.04 (2H, d, 8.7 Hz), 5.38 (1H, s), 2.96 (1H, s), 2.52 (3H, s), 1.37 (3H, s). 1H NMR (d6-DMSO d = 2.50): 8.59–8.64 (4H, m), 8.55 (2H, d, 8.1 Hz), 8.07 (2H, m), 7.75 (1H, t, 8.1 Hz), 7.70 (2H, ddd, 7.4, 5.5 and 1.2 Hz), 6.83 (2H, d, 8.6 Hz), 5.84 (2H, d, 8.6 Hz), 5.33 (1H, s), 3.76 (1H, s), 2.40 (3H, s), 1.28 (3H, s). 13C NMR (d6-DMSO d = 39.52): 186.2, 185.6, 160.8, 159.3, 154.2, 150.8, 136.4, 132.2, 128.6, 127.0, 125.4, 122.7, 121.4, 118.5, 108.4, 98.9, 85.1, 77.7, 28.1, 26.8. IR m/cm1 2178s (NCN) and 2095w (C„C). ES mass spectrum (CH3CN) m/z: 576 [M + H]+. Anal. Calc. for C29H23N5O2Ru(H2O)1,5: C, 57.9; H, 4.4; N, 11.6. Found: C, 58.0; H, 4.5; N, 11.6%. 4.3.3. Synthesis of [{Ru(tpy)(acac)}2(l-bcpda)] (4) Copper (I) chloride (2.0 mg, 0.020 mmol) was placed in a three-necked round bottom flask equipped with a stir bar, a water condenser and an adaptor connected to an oxygen source. Pyridine (6 ml) and 1,8-diazabicyclo[5.4.0]undec-7-ene (20 ll, 0.13 mmol) were added and the mixture was warmed to 40 C and vigorously stirred while bubbling oxygen. The initially yellow solution turned green after 10 min and [Ru(tpy)(acac)(epcyd)] (2) (60 mg, 0.10 mmol) was added. The reaction mixture was stirred at 40 C with oxygen bubbling for 1.5 h and then evaporated to dryness. The green residue was purified by column chromatography (weakly acidic alumina, solvent: dichloromethane, eluent: dichloromethane/ethanol 99:1 then 98.5:1.5). The second band (dark green) was collected and then evaporated to dryness to give a dark green powder of 4 (21 mg, 35%). 1H NMR (d6-DMSO, d = 2.50): 8.59–8.66 (8H, m); 8.55 (4H, d, 7.9 Hz); 8.08 (4H, m); 7.68–7.80 (6H, m); 6.90 (4H, d, 8.8 Hz); 5.86 (4H, d, 8.8 Hz); 5.33 (2H, s); 2.40 (6H, s); 1.28 (6H, s). IR m/cm1 2166s and 2133 (NCN). FAB mass spectrum (DMF) m/z: 1149 [M + H]+; 716 [Ru(tpy)(acac)(L 0 H) + H]+. Anal. Calc. for C58H44N10O4Ru2: C, 60.7; H, 3.9; N, 12.2. Found: C, 60.4; H, 4.2; N, 11.8%.
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4.3.4. Synthesis of [{Ru(tpy)(acac)}2(l-bcpea)] (5) 9,10-diethynylanthracene was first prepared: 9,10Bis[(trimethylsilyl)ethynyl]anthracene (55 mg, 0.15 mmol, 1 equiv.) was solubilized in the mixture of methanol/ diethylether (2:1, 12 ml) previously degassed with argon. To the obtained yellow solution was added a solution of potassium hydroxide in water (1.0 ml, 0.71 M). The mixture was stirred at 40 C under argon for 2.5 h and evaporated to dryness. The orange residue was dissolved in dry THF and used without any purification in the Sonogashira coupling reaction. [Ru(tpy)(acac)(Ipcyd)] (100 mg, 0.148 mmol), CuI (6.0 mg, 21 mol%) and Pd(PPh3)4 (11.1 mg, 6.5 mol%) were placed in the cosolvent DMF/piperidine (4:1, 5 ml) previously degassed with argon. The freshly prepared solution of 9,10-diethynylanthracene in THF was added and the initially blue-green solution turned instantly purple. The reaction mixture was stirred at room temperature for 3 h and then evaporated to dryness. The resulting purple solid was dissolved in dichloromethane and purified by column chromatography (weakly acidic alumina, solvent: dichloromethane, eluent: dichloromethane/ethanol 99:1 then 98:2). The second band (purple) was collected and then evaporated to dryness to give a dark purple powder of 5 (34 mg, 35%). 1H NMR (d6-DMSO, d = 2.50): 8.52–8.69 (16H, m); 8.10 (4H, dt, 7.7 and 1.6 Hz); 7.79 (2H, t, 8.0 Hz); 7.69–7.78 (8H, m); 7.24 (4H, d, 8.6 Hz); 6.03 (4H, d, 8.6 Hz); 5.35 (2H, s); 2.43 (6H, s); 1.30 (6H, s). IR m/cm1 2168s (NCN). ES mass spectrum (CH3CN) m/z: 1325 [M + H]+; 892 [[Ru(tpy)(acac)(L 0 H)] + H]+, 663 [M + 2H]2+. Anal. Calc. for C72H52N10O4Ru2(EtOH)(H2O)1,5: C, 63.6; H, 4.4; N, 10.0. Found: C, 64.0; H, 4.3; N, 9.6%.
4.4. Synthesis of ligands 4.4.1. Synthesis of hmbpcydH To a solution of IpcydH (1.00 g, 4.10 mmol), Pd(PPh3)4 (200 mg, 4 mol%) and CuI (160 mg, 20 mol%) in the previously degassed DMF/piperidine cosolvent (5:1, 30 ml) was added 2-methylbut-3-yn-2-ol (2.0 ml, 5 equivalents) under argon. The mixture was stirred for 1.5 h at room temperature and then evaporated to dryness. The remaining solid was purified by column chromatography (silica gel, solvent: dichloromethane, eluent: dichloromethane then dichloromethane/ethanol 98:2). The third band (yellow) was collected, evaporated to dryness and recrystallized from a dichloromethane/cyclohexane mixture to give a pale yellow powder of 2 0 (495 mg, 60%). 1H NMR (CD2Cl2 d = 5.35): 7.43 (2H, d, 8.9 Hz); 6.99 (2H, d, 8.9 Hz); 1.60 (6H, s). NMR1H (d6-DMSO d = 2.50): 7.36 (2H, d, 8.5 Hz); 6.93 (2H, d, 8.5 Hz); 5.45 (1H, s large); 1.44 (6H, s). IR m/cm1 2227s (C„N). EI mass spectrum (MeOH) m/z: 200 [M]+, 185 [M–CH3]+. Anal. Calc. for
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C12H12N2O(CH2Cl2)0,03: C, 71.3; H, 6.0; N, 13.8. Found: C, 71.5; H, 6.0; N, 13.7%. 4.4.2. Synthesis of epcydH A solution of hmbpcydH (490 mg, 2.45 mmol) and potassium tert-butoxide (360 mg, 3.21 mmol, 1.3 equivalents) in dimethylformamide (30 ml) was heated at 60 C for 1 h. At this stage, more potassium tert-butoxide (120 mg, 1.07 mmol, 0.4 equivalents) was added and the solution was stirred further for 1 h at 60 C. The mixture was then evaporated to dryness and dissolved in a mixture of dichloromethane (100 ml) and acetic acid (5 ml). This solution was washed with water (3 · 30 ml), dried over MgSO4 and evaporated to dryness. The residue was further purified by column chromatography (silica gel, solvent: dichloromethane, eluent: dichloromethane/ethanol 99:1) and recrystallized from a dichloromethane/cyclohexane mixture to afford a yellowish powder of 3 0 (240 mg, 69%). 1H NMR (CD2Cl2 d = 5.35): 7.51 (2H, d, 8.7 Hz); 7.02 (2H, d, 8.7 Hz); 6.36 (1H, s large); 3.15 (1H, s).1H NMR (d6-DMSO d = 2.50): 7.46 (2H, d, 8.8 Hz); 6.95 (2H, d, 8.8 Hz); 4.11 (1H, s). IR m/cm1 2230s (C„N) and 2105w (C„C). EI mass spectrum (MeOH) m/z: 142 [M]+. Anal. Calc. for C9H6N2 (H2O)0,02: C, 75.8; H, 4.3; N, 19.7. Found: C, 75.4; H, 4.4; N, 20.2%. 4.4.3. Synthesis of bcpdaH2 Copper (I) chloride (42 mg, 0.42 mmol) was placed in a three-necked round bottom flask equipped with a stir bar and an adaptor connected to an oxygen source. Pyridine (10 ml) and 1,8-diazabicyclo[5.4.0]undec-7-ene (0.65 ml, 4.3 mmol) were added and the mixture was warmed to 40 C and vigorously stirred while bubbling oxygen. The solution turned dark green after 10 min and epcydH (300 mg, 2.11 mmol) was added. The mixture was stirred at 40 C with oxygen bubbling for 1 h and then evaporated to dryness. The greenish residue was purified by column chromatography (silica gel, solvent: dichloromethane, eluent: dichloromethane/ethanol 99:1 then 97:3) and recrystallized from a dichloromethane/cyclohexane mixture to afford a yellow powder of 4 0 (53 mg, 18%). 1H NMR (d6-acetone d = 2.05): 7.60 (4H, d, 8.8 Hz); 7.11 (4H, d, 8.8 Hz); 9.20 (2H, s large). IR m/cm1 2227s and 2241sh (C„N). EI mass spectrum (MeOH) m/z: 282 [M]+. Anal. Calc. for C18H10N4 (H2O)0,1: C, 76.1; H, 3.6; N, 19.7. Found: C, 76.1; H, 3.8; N, 19.7%. 4.4.4. Synthesis of bcpeaH2 To a solution of IpcydH (100 mg, 0.410 mmol), Pd(PPh3)4 (22 mg, 4.6 mol%) and CuI (24 mg, 31 mol%) in the previously degassed cosolvent dimethylformamide/piperidine (3:1, 4 ml) was added 9,10-bis(3-hydroxy3-methylbutynyl)anthracene (68 mg, 0.20 mmol, 0.48 equivalents) and potassium tert-butoxide (112 mg,
1.06 mmol, 2.6 equivalents). After stirring for 1 h at 60 C, the reaction mixture initially yellow turned violet. At this stage, evaporation of the solution gave a solid, which was purified by column chromatography (silica gel, solvent: dichloromethane, eluent: dichloromethane/ ethanol 98:2 then 96:4) to yield a red powder of 5 0 (65 mg, 71%). 1H NMR (d6-acetone d = 2.05): 8.75 (4H, dd, 6.7 and 3.3 Hz); 7.89 (4H, d, 8.8 Hz); 7.74 (4H, dd, 6.7 and 3.3 Hz); 7.22 (4H, d, 8.8 Hz). IR m/cm1 2220s and 2234sh (CN). DCI mass spectrum (MeOH, NH3) m/z: 459 [M + H]+. Anal. Calc. for C32H18N4(H2O)0,6: C, 81.9; H, 4.1; N, 11.9. Found: C, 81.9; H, 4.1; N, 11.8%. 4.4.5. Synthesis of the tetraphenylarsonium salt of Ipcyd, [As(Ph)4][Ipcyd] IpcydH (200 mg, 0.820 mmol) was placed in a 2.0 M sodium hydroxide aqueous solution (10 ml) and the mixture was degassed and stirred under argon until complete dissolution. [As(Ph)4]Cl Æ H2O (400 mg, 0.955 mmol, 1.16 equivalents) was dissolved in a previously degassed 2.0 M sodium hydroxide aqueous solution (10 ml) and the resulting solution was transferred under argon to the basic solution of the ligand. The mixture was stirred for 0.5 h at room temperature and then the white precipitate was filtered, washed with water and vacuum dried to yield a white powder of the desired product (402 mg, 78%). 1H NMR (CD2Cl2 d = 5.35): 7.90 (4H, tt, 7.5 and 1.3 Hz); 7.78 (8H, m); 7.63 (8H, d, 7.3 Hz); 7.14 (2H, d, 8.9 Hz); 6.55 (2H, d, 8.9 Hz). IR m/cm1 2094s (NCN). ES mass spectrum (MeOH) m/z: 243 [Ipcyd], 383 [As(Ph)4]+. Anal. Calc. for C31H24N2IAs (H2O)2: C, 56.2; H, 4.3; N, 4.2. Found: C, 56.4; H, 4.1; N, 4.2%. 4.4.6. Synthesis of the tetraphenylarsonium salt of hmbpcyd, [As(Ph)4][hmbpcyd] The procedure was the same as for the synthesis of [As(Ph)4][Ipcyd] and a yellowish powder was obtained (65%). 1H NMR (CD2Cl2 d = 5.35): 7.90 (4H, tt, 7.4 and 1.3 Hz); 7.78 (8H, m); 7.63 (8H, d, 7.3 Hz); 6.98 (2H, d, 8.7 Hz); 6.65 (2H, d, 8.7 Hz); 1.56 (6H, s). IR m/cm1 2104s (NCN). ES mass spectrum (MeOH) m/z: 199 [hmbpcyd], 383 [As(Ph)4]+. Anal. Calc. for C36H31N2OAs (H2O)0,2: C, 73.7; H, 5.4; N, 4.8. Found: C, 73.6; H, 5.3; N, 4.8%. 4.4.7. Synthesis of the tetraphenylarsonium salt of epcyd, [As(Ph)4][epcyd] The procedure is identical to the synthesis of [As(Ph)4][Ipcyd] and a yellowish powder was obtained (69%). 1H NMR (CD2Cl2 d = 5.35): 7.90 (4H, tt, 7.4 and 1.3 Hz); 7.78 (8H, m); 7.63 (8H, d, 7.3 Hz); 7.07 (2H, d, 8.7 Hz); 6.66 (2H, d, 8.7 Hz); 2.95 (1H, s). IR m/cm1 2090s (NCN). ES mass spectrum (MeOH) m/z: 141 [epcyd], 383 [As(Ph)4]+. Anal. Calc. for C33H25
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N2As (H2O)0,4: C, 74.5; H, 4.9; N, 5.3. Found: C, 74.6; H, 4.7; N, 5.3%. 4.4.8. Synthesis of the tetraphenylarsonium salt of bcpda2, [As(Ph)4]2 [bcpda] The procedure was the same as for the synthesis of [As(Ph)4][Ipcyd] except that 2.4 equivalents of [As(Ph)4]Cl Æ H2O were used. A yellow powder was obtained (75%). 1H NMR (CD2Cl2 d = 5.35): 7.89 (8H, tt, 7.5 and 1.3 Hz); 7.77 (16H, m); 7.63 (16H, d, 7.2 Hz); 6.99 (4H, d, 8.8 Hz); 6.64 (4H, d, 8.8 Hz). IR m/cm1 2114s (NCN). ES mass spectrum (MeOH) m/z: 281 [LH], 383 [As(Ph)4]+. FAB mass spectrum (DMF) it m/z: 663 [L2, As(Ph)4+], 383 [As(Ph)4]+. Anal. Calc. for C66H48N4As2(H2O)3: C, 72.0; H, 4.9; N, 5.1. Found: C, 72.0; H, 4.8; N, 5.2%. 4.4.9. Synthesis of the tetraphenylarsonium salt of bcpea2, [As(Ph)4]2[bcpea] The procedure was similar to the synthesis of [As(Ph)4]2[bcpda] except that a mixture of 2.0 M NaOH aqueous solution and MeOH was used (5:1). A violet powder was obtained (78%). 1H NMR (CD2Cl2 d = 5.35): 8.65 (4H, dd, 6.5 and 3.3 Hz); 7.85 (8H, tt, 7.5 and 1.3 Hz); 7.72 (16H, m); 7.57 (4H, dd, 6.5 and 3.3 Hz); 7.55 (16H, d, 7.2 Hz); 7.38 (4H, d, 8.7 Hz); 6.84 (4H, d, 8.7 Hz). IR m/cm1 2099s and 2177s (NCN). ES mass spectrum (MeOH) m/z: 228 [L]2, 457 [LH], 383 [As(Ph)4]+. Anal. Calc. for C80H56N4As2(H2O)1,4: C, 77.0; H, 4.7; N, 4.5. Found: C, 76.8; H, 4.5; N, 4.3%. 4.5. Crystal structure determination of [Ru(tpy)(acac)(hmbpcyd)] (2) Dark blue needles were grown by slow evaporation of a mixture of an ethanol/water solution of the complex. The diffraction intensities were collected on a Nonius Kappa CCD diffractometer at room temperature, using graphite monochromated Mo Ka radiation ˚ ) at a detector distance of 4 cm. The crys(k = 0.71073 A tallographic cell was found by using EVAL-CCD [34]. The structure was solved using DIRDIFF [35] and refined in the maXus software package [36]. Absorption corrections were performed using SORTAV program Blessing 1995. The refinement was performed anisotropically for all the non-hydrogen atoms of the complex except for the oxygen of the water molecule. The hydrogen atoms were localized by difference Fourier ˚ , then their synthesis, recalculated and fixed at 0.97 A contributions were introduced in the calculations but not refined. 1526 reflections [I > 3r(I)] were used for the 375 parameters and the R value dropped to 0.040. The full experimental details, atomic parameters and the complete listing of bond lengths and angles are available as supplementary data.
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Acknowledgments The authors thank CNRS and MENRS (M.F.) for financial support, Yannick Coppel (Laboratoire de Chimie de Coordination LCC/CNRS) for the 13C NMR spectra, Christine Viala (CEMES) for technical assistance and Christophe Coudret (CEMES) for helpful advice.
Appendix A. Supplementary data 1
H and 13C NMR spectral data for [Ru(tpy)(acac)(hmbpcyd)] 2 in d6-DMSO (Table S1). 1H and 13 C NMR spectral data for [Ru(tpy)(acac)(epcyd)] (3) in d6-DMSO (Table S2). 1H NMR spectra of 2 in d6-DMSO at 293 K (Figure S1). Cyclic voltammogram of 2 in DMF containing 0.1 M TBAH in the range 1.8:+0.8 V (Figure S2). Differential pulse voltammogram of 2 in DMF containing 0.1 M TBAH in the range 1.8:+1.5 V (Figure S3). UV–Vis spectra of the tetraphenylarsonium salts of the phenylcyanamide derivative ligands in DMF (Figure S4). Comparison of the electronic absorption spectra of complex 4 and [AsPh4]2[bcpda] in DMF (Figure S5). Comparison of the electronic absorption spectra of complex 5 and [AsPh4]2[bcpea] in DMF (Figure 6). Stepwise spectroelectrochemical oxidation and reduction of 4 and 42+in DMF containing 0.1 M TBAH (Figures S7 and S8). X-ray crystallographic files in CIF format for the structure determination of 2, CCDC 235561. These data can be obtained free of charge via www.ccdc. cam.ac.uk/data_request/cif, by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.’’ Supplementary data associated with this article can be found, in the online version, at doi:10.1016/ j.ica.2005.01.004.
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[24] L.J. Farrugia, J. Appl. Cryst. I (1997) 565. [25] R.J. Crutchley, K. McCaw, F.L. Lee, E.J. Gabe, Inorg. Chem. 29 (14) (1990) 2576. [26] C.E.B. Evans, G.P.A. Yap, R.J. Crutchley, Inorg. Chem. 37 (24) (1998) 6161. [27] A.R. Rezvani, C. Bensimon, B. Cromp, C. Reber, J.E. Greedan, V.V. Kondratiev, R.J. Crutchley, Inorg. Chem. 36 (15) (1997) 3322. [28] W. Zhang, C. Bensimon, R.J. Crutchley, Inorg. Chem. 32 (25) (1993) 5808. [29] D.R. Coulson, Inorg. Synth. 13 (1972) 121. [30] J.A.H. MacBride, K. Wade, Synth. comm. 26 (1996) 2309. [31] B.F. Duerr, Y.-S. Chung, A.W. Czarnik, J. Org. Chem. 53 (1988) 2120. [32] E. Kobayashi, J. Jiang, J. Furukawa, Polym. J. 1990 (22) (1990) 266. [33] C. Patoux, C. Coudret, J.-P. Launay, C. Joachim, A. Gourdon, Inorg. Chem. 36 (1997) 5037. [34] A.J.M. Duisenberg, Reflections on Area Detectors. Utrecht, 1998. [35] P.T. Beurskens, G. Beurskens, R. de Gelder, S. Garcia-Granda, R.O. Gould, R. Israel, J.M.M. Smits, The DIRDIF-99 Program System, University of Nijmegen, The Netherlands, 1999. [36] S. Mackay, C.J. Gilmore, C. Edwards, N. Stewart, K. Shankland, maXus Computer Program for the Solution and Refinement of Crystal Structures, in: MaXus Computer Program for the Solution and Refinement of Crystal Structures, Nonius, MacScience/the University of Glasgow, The Netherlands/Japan, 1999.
Synthesis of novel mononuclear and dinuclear ruthenium(II) complexes with terpyridine and acetylacetonate ancillary ligands and cyanamide derivative ligands Muriel A. Fabre, Joe¨l Jaud, Jacques J. Bonvoisin
*
CEMES/CNRS – NanoSciences Group, 29 rue Jeanne Marvig, BP 94347, 31055 Toulouse Cedex 4, France Received 9 December 2004; accepted 11 January 2005 Available online 7 February 2005
Abstract Several new mononuclear and dinuclear ruthenium(II) complexes – incorporating 2,2 0 :6 0 ,200 -terpyridine and acetylacetonate as ancillary ligands and phenylcyanamide derivative ligands – of the type [Ru(tpy)(acac)(L)] and [{Ru(tpy)(acac)}2(l-L 0 )] (where tpy = 2,2 0 :6 0 ,200 -terpyridine, acac = acetylacetonate, L = hmbpcyd = 4-(3-hydroxy-3-methylbutynyl)phenylcyanamide anion (2) and epcyd = 4-ethynylphenylcyanamide anion (3) and L 0 = bcpda = bis(4-cyanamidophenyl)diacetylene dianion (4) and bcpea = 9,10bis(4-cyanamidophenylethynyl)anthracene dianion (5)) were synthesized in a stepwise manner starting from [Ru(tpy)(acac)(Ipcyd)] (1), where Ipcyd = 4-iodophenylcyanamide anion. Tetraphenylarsonium salts of the phenylcyanamide derivative ligands were also prepared. The four complexes have been characterized by UV–Vis, IR, ES-MS, electrochemistry and 1H NMR. Mononuclear complexes 2 and 3 were further characterized by 13C NMR. The single crystal X-ray structure of 2 was determined, it crystallized with one molecule of water with empirical formula of C32H31N5O5Ru, in a monoclinic crystal system and space group of P21/n with ˚ , b = 9.634(2) A ˚ , c = 20.063(7) A ˚ , b = 92.65(3), V = 3406(2) A ˚ 3 and Z = 4. The structure was refined to a final R faca = 17.642(5) A tor of 0.040. The Ru(III/II) couple of 1–3 appeared around 0.34 V versus the saturated calomel electrode in dimethylformamide and at a slightly higher potential, around 0.36–0.37 V for 4 and 5. Spectroelectrochemical studies were also performed for 4 and 5, no intervalence transition was observed despite all attempts. 2005 Elsevier B.V. All rights reserved. Keywords: Molecular electronics; Mononuclear and dinuclear ruthenium(II) complexes; Cyanamide derivatives; X-ray structure; Spectroelectrochemical studies
1. Introduction In the molecular electronics field, it is important to evaluate the capacity of a molecule to conduct electrons. A possible way is to synthesize bimetallic complexes where the molecule to test is a bridging ligand or a spacer between two metallic sites [1,2]. The electronic communication between two metallic centers through a bridging ligand can then be assessed by the electronic *
Corresponding author. Tel.: +33 5 62 25 78 52; fax: +33 5 62 25 79
99. E-mail address: [email protected] (J.J. Bonvoisin). 0020-1693/$ - see front matter 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2005.01.004
coupling parameter Vab in the mixed valence form [3]. However, the method, which consists of measuring the parameter Vab by UV–Vis near IR spectroscopy through the intervalence transition [4], has experimental limits. ˚ For long molecules (with a distance greater than 25 A between the two redox centers), the intervalence transition becomes almost undetectable. An alternative could be to measure the magnetic coupling parameter J between the two metallic centers through the bridging ligand in the paramagnetic homovalent form of the dinuclear complex [5–7]. This parameter can be given by magnetic susceptibility or EPR techniques. The correlation between the two parameters Vab and J has still
M.A. Fabre et al. / Inorganica Chimica Acta 358 (2005) 2384–2394
to be settled. First, good candidates have to be found, where the interactions are strong enough to be measurable in both forms (mixed-valence and paramagnetic homovalent) of the dinuclear complexes. Crutchley [5] showed that cyanamide (NCN) groups included in a bridging ligand were particularly well suited to promote such strong interactions between two metallic sites either in homovalent [8] or mixed-valence [9,10] ruthenium complexes. Recent theoretical studies performed by Ruiz and coworkers corroborate this point and conclude that dicyd-type bridging ligands constitute interesting goals for obtaining strong exchange coupling of paramagnetic ions at very long distance [11]. Previous work showed that dinuclear ruthenium complexes with a phenylcyanamide derivative as bridging ligand and terpyridine, bipyridine as ancillary ligands are not suitable for this purpose, the bridging ligand being oxidized before the ruthenium(II) atoms [7,12] due presumably to the acceptor character of the bipyridine ligand. This led us to replace the bipyridine ligand by a donor group such as acetylacetonate, which has shown its capacity to tune the redox potential of ruthenium complexes [13]. Following this line, we succeeded to synthesize a neutral building block [Ru(tpy)(acac)(Ipcyd)] (where Ipcyd = 4-iodophenylcyanamide) and incidentally a ruthenium complex containing a zwitterionic form of the phosphoniophenylcyanamide ligand [14]. Here, we present the successful synthesis of four new ruthenium complexes starting from [Ru(tpy)(acac)(Ipcyd)] (1): two mononuclear complexes, [Ru(tpy)(acac)(L)], where L = hmbpcyd = 4-(3hydroxy-3-methylbutynyl)phenylcyanamide anion (2) and epcyd = 4-ethynylphenylcyanamide anion (3), and two dinuclear complexes, [{Ru(tpy)(acac)}2(l-L 0 )], where L 0 = bcpda = bis(4-cyanamidophenyl)diacetylene dianion (4) and bcpea = 9,10-bis(4-cyanamidophenylethynyl)anthracene dianion (5). Optical and electrochemical properties of 1–5 are reported and compared. The spectroelectrochemical properties of complexes 4 and 5 are also reported. The free phenylcyanamide derivative ligands in their deprotonated form (tetraphenylarsonium salts) are also presented here for the sake of a better understanding of the spectroscopic and electrochemical properties of the corresponding complexes.
2. Results and discussion 2.1. Synthesis The synthesis of [Ru(tpy)(acac)(epcyd)] (3) from [Ru(tpy)(acac)(Ipcyd)] (1) in two steps via [Ru(tpy)(acac)(hmbpcyd)] (2) was adapted from literature procedures [15]. The carbinol-protected alkyne complex [Ru(tpy)(acac)(hmbpcyd)] (2) was prepared by a Sono-
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gashira cross-coupling reaction between the iodoruthenium complex [Ru(tpy)(acac)(Ipcyd)] (1) and 2methylbut-3-yn-2-ol under classic conditions (Pd(PPh3)4, CuI, piperidine, and DMF). The ethynylated complex [Ru(tpy)(acac)(epcyd)] (3) could then be obtained by a deprotection reaction of [Ru(tpy)(acac)(hmbpcyd)] (2) by tBuOK in DMF. [Ru(tpy)(acac)(epcyd)] (3) was then used as a synthon in a homo-coupling reaction to form the diyne dinuclear complex [{Ru(tpy)(acac)}2(l-bcpda)] (4). This reaction was performed using DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) and copper(I) chloride in dry pyridine with oxygen bubbling [16]. A general scheme is shown in Scheme 1. Complex [{Ru(tpy)(acac)}2(l-bcpea)] (5) was synthesized by a Sonogashira cross-coupling reaction between the iodoruthenium complex [Ru(tpy)(acac)(Ipcyd)] (1) and 9,10-diethynylanthracene under classic conditions (Scheme 2). It has to be noted that complexes 4 and 5 are poorly soluble in every solvent. The best solubility was found with DMF, which is why all spectroscopic and electrochemical studies were performed in this solvent. The free phenylcyanamide derivative ligands were also synthesized in order to have a better understanding of the physico-chemical properties of the complexes. First, the ligands were prepared in their neutral protonated form from IpcydH, using the same coupling reaction conditions as for the complexes (Scheme 3). The tetraphenylarsonium salts of the anionic deprotonated ligands were then obtained according to a general procedure [8]. 2.2. Electrochemical studies Cyclic voltammograms of the tetraphenylarsonium salts of the anionic ligands and of the complexes were recorded in dimethylformamide under an argon atmosphere with 0.1 M tetrabutylammonium hexafluorophosphate (TBAH). Cyclic voltammetry data for the investigated species are given in Table 1. The E1/2 potentials were determined from the average of the anodic and cathodic peak potentials for reversible waves. For irreversible waves, the anodic peak potentials are reported. The voltammograms of the tetraphenylarsonium salts of the free anionic ligands present an irreversible wave in oxidation around 0.5 V. The three mononuclear complexes (1, 2 and 3) present very similar voltammetric behaviors. The voltammograms show two waves in oxidation (Fig. 1). The first wave at 0.34 V was attributed to the Ru(II/III) couple. As shown in the inset of Fig. 1, this wave became quasi-reversible when scan range was decreased to 0.8 V, with peak to peak separation of 78 mV independent of scan rate from 0.1 to 1.0 V/s. The second wave around 1.1 V is irreversible. It is very probably due to the
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M.A. Fabre et al. / Inorganica Chimica Acta 358 (2005) 2384–2394 N N N
I
N
Ru
N
2-methylbut-3-yn-2-ol N
O DMF/piperidine
O
N
OH
Pd(PPh3)4/CuI
N
N Ru
O O
N
2 77%
1
tBuOK DMF N
O O
Ru N N
N N N
N N
N DBU CuCl, O2
N Ru
O pyridine
O
N
N N
H
N Ru
O O
N
4
3
35%
60%
Scheme 1. General scheme for the synthesis of complexes 2, 3 and 4.
O O
H N N N
H N
N Ru
O O
N
CuI, Pd(PPh3)4 DMF/piperidine
Ru N N
I
N N
N
N
N Ru
N
N
O O
5 1
35%
Scheme 2. Synthesis of [{Ru(tpy)(acac)}2(l-bcpea)] (5).
irreversible oxidation of the phenylcyanamide anionic ligand as it was demonstrated in a previous study on [Ru(tpy)(bpy)(Ipcyd)] [12]. It is also confirmed by the study of the tetraphenylarsonium salts of the ligands. The ligands being stabilized when coordinated to the Ruthenium (III) center, their oxidation shifts anodically (1.1 V versus 0.5 V). In reduction, a quasi-reversible wave around 1.58 V was observed and assigned to the reduction of the terpyridine ligand (see Supporting Information Figure S2 and S3). The voltammograms of the two dinuclear complexes 4 and 5 are quite the same but the Ru(II/III) couple appears at a slightly higher potential (0.36–0.37 V) than the mononuclear complexes 1, 2 and 3 (0.34 V). The anodic shift observed for dinuclear complexes is proba-
bly due to a better conjugation of the bridging ligand decreasing its donor properties and leaving the ruthenium center harder to oxidize. Only one quasi-reversible Ru(II/III) couple is seen, due to the weak coupling between the metal ions and the resultant superimposition of the two one-electron Ru(II/III) couples. At this point, it has to be noted that a single electrochemical wave observed for both dinuclear complexes 4 and 5 does not mean that mixed-valence species are not present in solution [1,17]. Even, in very large systems, where the distance between the metallic sites reaches nanometer size, the comproportionation constant (Kc) tends toward a statistical limit of 4 and at half oxidation, the proportion of mixed-valence species reaches a comfortable 50%.
M.A. Fabre et al. / Inorganica Chimica Acta 358 (2005) 2384–2394 H H
OH
Pd(PPh3)4/CuI N
H
I
tBuOK
H
N OH
DMF/piperidine
N
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DMF
N
IpcydH
N
N
epcydH
hmbpcydH 60%
H
H
69%
H
DBU CuCl, O2 pyridine
Pd(PPh3)4/CuI
DMF/piperidine N
N H
N
N
H N
H
N H
N
N
bcpdaH2 18%
bcpeaH2 71%
Scheme 3. Synthesis of the free phenylcyanamide derivative ligands.
Table 1 Electrochemical data, versus SCE, in DMF, 0.1 M TBAH, 0.1 V/s Species
Oxidation Ru
[As(Ph)4][Ipcyd] [As(Ph)4][hmbpcyd] [As(Ph)4][epcyd] [As(Ph)4]2[bcpda] [As(Ph)4]2[bcpea] 1 2 3 4 5
II/III
, E1/2, V (DE, mV)
– – – – – 0.337 (78) 0.337 (78) 0.342 (78) 0.373 (83) 0.355(83)
Ligand, Ea (V) 0.503 0.483 0.527 0.488 0.474 1.141 1.138 1.162 1.150 1.001
Reduction tpy, E1/2, V (DE, mV) – – – – – 1.588 1.574 1.579 1.569 1.595
(78) (73) (73) (74) (93)
E1/2 = (Ea + Ec)/2; dE = jEa Ecj; Ea: anodic peak potential; Ep: cathodic peak potential.
2.3. Electronic absorption 1.20E-06 5.00E-07
i (A)
9.00E-07
1.00E-07
6.00E-07
-3.00E-07 0
0.2
0.4
0.6
0.8
3.00E-07
0.00E+00
-3.00E-07 0
0.2
0.4
0.6
0.8
1
1.2
1.4
E (V/sce) Fig. 1. Cyclic voltammogram of complex 2, platinum disk working electrode, 0.1 M TBAH in DMF, scan rate 0.1 V/s [scan range: 0 ! +1.5 ! 0 V]; Insert: Cyclic voltammogram of complex 2 [scan range: 0 ! +0.8 ! 0 V].
Electronic absorption data of the tetraphenylarsonium salts of the free ligands and of the complexes have been placed in Table 2. The spectra of the free ligands have been placed in the Supporting Information, Figure S4. The monocyanamide ligands mainly present an intense absorption band around 300 nm, which is attributable to p ! p* transitions. The intensity of this band is almost identical for the three monocyanamide ligands Ipcyd, hmbpcyd, and epcyd (34–37 · 103 M1 cm1) but it has to be noticed that it shifts toward higher wavelengths when the p system of the ligand is increased (292 nm for [As(Ph)4][Ipcyd] versus 320 and 324 nm for [As(Ph)4][hmbpcyd] and [As(Ph)4][epcyd], respectively). The spectrum of biscyanamide ligand [bcpda]2 shows two bands at 377 and 408 nm. The spectrum of biscyanamide ligand [bcpea]2 shows two bands in the UV region (296 and 344 nm) and a broader and more intense band at 560 nm.
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Table 2 UV–Vis absorption data of the investigated compounds Species
Absorption bands,a k in nm (e · 103 in M1 cm1)
[As(Ph)4][Ipcyd] [As(Ph)4][hmbpcyd] [As(Ph)4][epcyd] [As(Ph)4]2[bcpda] [As(Ph)4]2[bcpea] 1
292 (34), 326sh (4.4) 320 (37) 324 (34) 377 (74), 408 (64) 296 (36), 344 (39), 560 (58) 278 (26), 317 (25), 372sh (9.0), 564 (4.9), 607 (4.6) 275 (45), 320 (52), 390sh (12), 568 (5.9), 631 (5.4) 274 (44), 320 (49), 390sh(14), 564 (6.1), 608 (5.7) 277 (63), 319 (62), 399 (66) 408 (66), 564 (10), 630 (9.2) 275 (61), 323 (61), 372sh (39), 492 (9.3), 940sh (17), 1086 (20) 320 (63), 438 (20), 556 (44) 318 (53), 491 (42), 862 (11), 1140 (14)
2 3 4 42+ 5 52+ a
In DMF.
The spectra of complexes 1, 2, 3 and 4 in dimethylformamide (Fig. 2) showed two broad bands in the visible region, which can be assigned to dp(Ru(II)) ! p*(tpy) MLCT transitions [12,14]. This hypothesis is confirmed by the fact that their intensities are almost constant in the three mononuclear complexes and nearly twice the same in the dinuclear complex 4. The two intense bands (around 280 and 320 nm) are attributable to the terpyridine ligand (p ! p* transitions), probably with a superposition of p ! p* transitions of the ligand L in the case of mononuclear complexes 2 and 3, all the more so, since the free deprotonated ligands L of these two complexes show a band in this region. The band that lies between 372 and 390 nm is more controversial. The spectrum of the dinuclear complex 4 shows an additional double band around 400 nm, which we tentatively assign to p ! p* transitions of the bridging ligand L 0 , since the free deprotonated ligand presents two bands
in this region (see also Figure S5 in the Supporting Information). The spectrum of the dinuclear complex 5 also shows two intense bands corresponding to the p ! p* transitions of the terpyridine ligand and one broad and quite intense band at 556 nm, which could be attributed to a superposition of (dp(Ru(II)) ! ptpy) MLCT transitions and intraligand transitions of the bridging ligand L 0 (see also Figure S6 in the Supporting Information). 2.4. Spectroelectrochemistry Spectroelectrochemical studies of the [II,II] dinuclear complex 5 were performed in dimethylformamide to generate [II,III] and [III,III] spectra and are shown in Fig. 3, while the spectra resulting from the stepwise oxidation of dinuclear complex 4 have been placed in the Supporting Information (Figure S7). During the electrochemical oxidation of dinuclear complex 4, the two broad bands at 564 and 630 nm (dp(Ru(II)) ! p*(tpy) MLCT transitions) decrease and one broad band, which can be attributed to a p(L 0 ) ! dp (Ru(III)) LMCT transition, appears at 1086 nm. During the oxidation of complex 5, the bands at 438 and 556 nm decrease and disappear completely, while three bands appear at 491, 862 and 1140 nm. The two broad bands at 862 and 1140 nm can be assigned to the Ru(III)-cyanamide LMCT chromophore. The sharp band at 491 nm could probably be attributed to ILCT. Further studies were performed to try to find a potential intervalence MMCT transition but no additional band could be detected upon oxidation of the dinuclear complexes 4 and 5. These transitions should exist but are probably very weak due to the great distance between the two rutheniums, respectively, 21.7 ˚ (calculated distances) and/or masked by and 25.7 A LMCT transitions. This lack of intervalence transition was not expected, and more specifically for complex 5 because the anthracene unit is supposed to play a special role in mediating electronic effect [18–22] and claimed to be a metal-to-metal communication amplifier when inserted into acetylene linkers [23]. 5
ε/104 (M-1.cm-1)
4 3 2 1 0 350
600
850
1100
1350
1600
1850
λ (nm)
Fig. 2. UV–Vis Spectra of complexes 1, 2, 3, 4 and 5 in DMF.
Fig. 3. Stepwise spectroelectrochemical oxidation of 5 in 0.1 M TBAH in DMF (electrolysis at 0.75 V vs. SCE).
M.A. Fabre et al. / Inorganica Chimica Acta 358 (2005) 2384–2394 Table 3 Crystallographic data and refinement parameters for 2 Formula Crystal system Formula weight (g mol1) Space group ˚) a (A ˚) b (A ˚) c (A b () ˚ 3) V (A Z l (Mo Ka) (mm1) qcalc (g cm3) 2hmax () Total number of reflections Number of unique reflections with I > 3r(I) Absorption correction Tmin/max Rfa Rwb Goodness-of-fit P P a Rf = iFoj jFci/ jFo j. 1=2 P P b Rw ¼ ð wjF o j jF c jÞ2 = wjF o j2 :
C32H29N5O3Ru, H2O monoclinic 650.7 P21/n 17.642(5) 9.634(2) 20.063(7) 92.65(3) 3406(2) 4 0.5 1.269 64 6847 1526 multi-scan 0.538/1.261 0.040 0.113 1.087
2.5. X-ray structure Crystal structure data for [Ru(tpy)(acac)(hmbpcyd)] Æ H2O (2) and selected bond lengths and angles are, respectively, given in Tables 3 and 4. Fig. 4 shows the ORTEP [24] drawing of 2 and the numbering scheme
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Table 4 ˚ ) and bond angles () for 2 Selected bond lengths (A Bond lengths Ru(1)–O(1) Ru(1)–N(1) Ru(1)–N(3) N(4)–C(21) N(5)–C(22) Bond angles O(1)–Ru(1)–O(2) O(1)–Ru(1)–N(2) O(1)–Ru(1)–N(4) O(2)–Ru(1)–N(2) O(2)–Ru(1)–N(4) N(1)–Ru(1)–N(3) N(2)–Ru(1)–N(3) N(3)–Ru(1)–N(4) Ru(1)–O(2)–N(2) N(4)–C(21)–N(5)
2.107(5) 2.077(6) 2.081(7) 1.115(9) 1.416(9) 91.4(2) 176.3(3) 87.4(2) 91.2(2) 177.1(2) 159.9(3) 79.6(3) 86.3(2) 42.7(2) 176.2(9)
Ru(1)–O(2) Ru(1)–N(2) Ru(1)–N(4) N(5)–C(21) C(28)–C(29) O(1)–Ru(1)–N(1) O(1)–Ru(1)–N(3) O(2)–Ru(1)–N(1) O(2)–Ru(1)–N(3) N(1)–Ru(1)–N(2) N(1)–Ru(1)–N(4) N(2)–Ru(1)–N(4) Ru(1)–O(2)–N(1) Ru(1)–N(4)–C(21) C(21)–N(5)–C(22)
2.059(5) 1.939(6) 2.060(6) 1.332(10) 1.188(11) 97.1(3) 103.0(3) 87.5(2) 91.4(2) 80.4(3) 95.3(2) 90.2(2) 46.5(2) 163.6(6) 114.2(6)
used in Table 4. It has to be noticed that the angle between the cyanamide group and the ruthenium atom, i.e., Ru(1)–N(4)–C(21), is 163.6(6), a value which is close to the one obtained for the dinuclear Ru(II) complex [{Ru(tpy)(bpy)}2(l-adpc)]2+ (164.4(2)) [9]. This is in contrast with the value obtained for [Ru(tpy)(bpy)(Ipcyd)]+ [12] (174.5(3)) as well as the ones obtained in the four known crystal structures of Ru(III)-cyanamide complexes [8,25–27], which show an average Ru(III)cyanamide bond angle of 174.6. This has been
Fig. 4. ORTEP drawing of complex [Ru(tpy)(acac)(hmpcyd)] Æ H2O (2) along with the atom numbering scheme (probability level of 30%).
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tentatively explained by a less good p bonding between the ruthenium (II) ion and the cyanamide group, which favors in that case a more bent structure [28]. This may also explain the sharper angle between the cyanamide group and the phenyl group for complex 2, i.e., C(21)– N(5)–C(22) = 114.2(6) compared to the one observed for [Ru(tpy)(bpy)(Ipcyd)]+, which is 120.4(4). One other point to be noticed is that the distance between N(4) and C(21) is the smallest one observed ˚ ), on all the above cited crystal structures (1.115(9) A and suggests a great deal of triple-bond character.
3. Conclusion The present paper illustrates the potentiality of the building block [Ru(tpy)(acac)(Ipcyd)] (1) to give novel mononuclear (2, 3) and dinuclear (4, 5) ruthenium complexes containing cyanamide derivatives. It also shows that the acetylacetonate ligand is definitively well suited to give access to the Ru(III) oxidation state. Spectroelectrochemical studies on dinuclear complexes 4 and 5 did not give the expected results: no intervalence transition in the mixed-valence state could be clearly observed, not even in the presence of a metal-to-metal amplifier unit like the anthracene group. This could be due to the weakness of the IT (given the large inter˚ ) and/or to metallic distance, which is greater than 20 A its being hidden by LMCT transitions. What remains to be done in the near future is to explore the magnetic properties of the now accessible Ru(III)–Ru(III) state of complexes 4 and 5.
4. Experimental 4.1. Materials All chemicals and solvents were of reagent grade or better. IpcydH [12], [Ru(tpy)(acac)(Ipcyd)] [14], tetrakis(triphenylphosphine)palladium(0) [29], 9,10bis(3-hydroxy-3-methylbutynyl)anthracene [18,30] and 9,10-bis[(trimethylsilyl)ethynyl]anthracene [31,32] were prepared according to the literature procedures. Weakly acidic Brockmann I type alumina (Aldrich) and Silica gel 60 (Fluka) were used. 4.2. Physical measurements UV–Vis spectra were recorded on a Shimadzu UV3100 spectrophotometer. 1H NMR spectra were recorded on a Bruker WF-250 spectrometer in CD2Cl2, d6-DMSO, d6-acetone and 13C NMR spectra on a Bruker AMX-500 in d6-DMSO. IR spectra of samples in KBr pellets were taken on a Perkin-Elmer 1725 FT-IR spectrophotometer. Mass spectra were recorded by the
Service de Spectroscopie de Masse of Universite´ Paul Sabatier using FAB (NBA matrix), DCI, EI (Nermag R10-R10) or ES in positive mode (Perkin-Elmer Sciex System API 365). Cyclic voltammograms were obtained with an Autolab system (PGSTAT 100) in dry dimethylformamide (0.1 M tetrabutylammonium hexafluorophosphate, TBAH) at 25 C with a three-electrode system consisting of platinum-disk working (1 mm diameter), platinum-wire counter and saturated calomel reference electrodes. Electrochemical oxidation for complexes 4 and 5 was performed by electrolysis with coulometry in dry dimethylformamide (DMF) (0.1 M TBAH) at 25 C at fixed potential (0.75 V vs SCE) with a three-electrode system consisting of platinum-net working, platinum-wire counter and saturated calomel reference electrodes [33]. 4.3. Synthesis of complexes 4.3.1. Synthesis of [Ru(tpy)(acac)(hmbpcyd)] (2) To a solution of [Ru(tpy)(acac)(Ipcyd)] (1) (170 mg, 0.256 mmol), Pd(PPh3)4 (20 mg, 7 mol%) and CuI (9 mg, 18 mol%) in the previously degassed DMF/piperidine cosolvent (3:1, 4 ml) was added 2-methylbut-3-yn2-ol (0.3 ml, 12 equivalents) under argon and the mixture was reacted for 2 h at room temperature. The solution was then evaporated to dryness. The resulting solid was dissolved in dichloromethane and was purified by column chromatography (weakly acidic alumina, solvent: dichloromethane, eluent: dichloromethane/ethanol 99:1 then 98:2). The second band (dark blue) was collected and then evaporated to dryness to give a dark blue powder of 2 (124 mg, 77%). 1H NMR (see Supporting Information, Figure S1 and Table S1) (CD2Cl2 d = 5.35): 8.73 (2H, ddd, 5.5, 1.5 and 0.8 Hz), 8.19 (2H, ddd, 8.1, 1.5 and 0.8 Hz), 8.11 (2H, d, 8.0 Hz), 7.92 (2H, ddd, 8.1, 7.6 and 1.5 Hz), 7.59 (1H, t, 8.0 Hz), 7.56 (2H, ddd, 7.6, 5.5 and 1.5 Hz), 6.87 (2H, d, 8.6 Hz), 6.02 (2H, d, 8.6 Hz), 5.38 (1H, s), 2.52 (3H, s), 1.55 (6H, s), 1.37 (3H, s). 1H NMR (d6-DMSO d = 2.50): 8.58–8.64 (4H, m), 8.55 (2H, d, 8.1 Hz), 8.07 (2H, ddd, 8.1, 7.5 and 1.4 Hz), 7.74 (1H, t, 8.1 Hz), 7.70 (2H, ddd, 7.5, 5.8 and 1.1 Hz), 6.74 (2H, d, 8.6 Hz), 5.82 (2H, d, 8.6 Hz), 5.33 (1H, s), 5.24 (1H, s), 2.40 (3H, s), 1.39 (6H, s), 1.27 (3H, s).13C NMR (d6-DMSO d = 39.52): 186.2, 185.6, 160.8, 159.4, 153.4, 150.8, 136.4, 131.7, 128.6, 127.0, 125.7, 122.7, 121.4, 118.5, 109.6, 98.9, 93.2, 81.6, 63.7, 32.0, 28.1, 26.8. IR m/cm1 2176s (NCN). ES mass spectrum (CH3CN) m/z: 634 [M + H]+. Anal. Calc. for C32H29N5O3Ru(H2O)1,5: C, 58.3; H, 4.9; N, 10.6. Found: C, 58.0; H, 4.7; N, 10.4%. 4.3.2. Synthesis of [Ru(tpy)(acac)(epcyd)] (3) To a solution of [Ru(tpy)(acac)(hmbpcyd)] (220 mg, 0.348 mmol) in dimethylformamide (9 ml) previously de-
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gassed was added potassium tert-butoxide (44 mg, 0.39 mmol, 1.1 equiv.) under argon. The mixture was heated at 70 C for 1 h and then evaporated to dryness. The dark blue residue was dissolved in 100 ml dichloromethane and washed with water (3 · 30 ml). The organic layer was dried on MgSO4 and evaporated to dryness. The resulting solid was purified by column chromatography (weakly acidic alumina, solvent: dichloromethane, eluent: dichloromethane/ethanol 99:1). The first band (dark blue) was collected, evaporated to dryness and recrystallized from a mixture of dichloromethane and hexane to give a dark blue microcrystalline powder of 3 (120 mg, 60%). 1H NMR (see Supporting Information, Table S2) (CD2Cl2 d = 5.35): 8.73 (2H, ddd, 5.5, 1.6 and 0.8 Hz), 8.17 (2H, ddd, 8.1, 1.4 and 0.8 Hz), 8.08 (2H, d, 8.0 Hz), 7.90 (2H, ddd, 8.1, 7.5 and 1.6 Hz), 7.57 (1H, t, 8.0 Hz), 7.55 (2H, ddd, 7.5, 5.5 and 1.4 Hz), 6.95 (2H, d, 8.7 Hz), 6.04 (2H, d, 8.7 Hz), 5.38 (1H, s), 2.96 (1H, s), 2.52 (3H, s), 1.37 (3H, s). 1H NMR (d6-DMSO d = 2.50): 8.59–8.64 (4H, m), 8.55 (2H, d, 8.1 Hz), 8.07 (2H, m), 7.75 (1H, t, 8.1 Hz), 7.70 (2H, ddd, 7.4, 5.5 and 1.2 Hz), 6.83 (2H, d, 8.6 Hz), 5.84 (2H, d, 8.6 Hz), 5.33 (1H, s), 3.76 (1H, s), 2.40 (3H, s), 1.28 (3H, s). 13C NMR (d6-DMSO d = 39.52): 186.2, 185.6, 160.8, 159.3, 154.2, 150.8, 136.4, 132.2, 128.6, 127.0, 125.4, 122.7, 121.4, 118.5, 108.4, 98.9, 85.1, 77.7, 28.1, 26.8. IR m/cm1 2178s (NCN) and 2095w (C„C). ES mass spectrum (CH3CN) m/z: 576 [M + H]+. Anal. Calc. for C29H23N5O2Ru(H2O)1,5: C, 57.9; H, 4.4; N, 11.6. Found: C, 58.0; H, 4.5; N, 11.6%. 4.3.3. Synthesis of [{Ru(tpy)(acac)}2(l-bcpda)] (4) Copper (I) chloride (2.0 mg, 0.020 mmol) was placed in a three-necked round bottom flask equipped with a stir bar, a water condenser and an adaptor connected to an oxygen source. Pyridine (6 ml) and 1,8-diazabicyclo[5.4.0]undec-7-ene (20 ll, 0.13 mmol) were added and the mixture was warmed to 40 C and vigorously stirred while bubbling oxygen. The initially yellow solution turned green after 10 min and [Ru(tpy)(acac)(epcyd)] (2) (60 mg, 0.10 mmol) was added. The reaction mixture was stirred at 40 C with oxygen bubbling for 1.5 h and then evaporated to dryness. The green residue was purified by column chromatography (weakly acidic alumina, solvent: dichloromethane, eluent: dichloromethane/ethanol 99:1 then 98.5:1.5). The second band (dark green) was collected and then evaporated to dryness to give a dark green powder of 4 (21 mg, 35%). 1H NMR (d6-DMSO, d = 2.50): 8.59–8.66 (8H, m); 8.55 (4H, d, 7.9 Hz); 8.08 (4H, m); 7.68–7.80 (6H, m); 6.90 (4H, d, 8.8 Hz); 5.86 (4H, d, 8.8 Hz); 5.33 (2H, s); 2.40 (6H, s); 1.28 (6H, s). IR m/cm1 2166s and 2133 (NCN). FAB mass spectrum (DMF) m/z: 1149 [M + H]+; 716 [Ru(tpy)(acac)(L 0 H) + H]+. Anal. Calc. for C58H44N10O4Ru2: C, 60.7; H, 3.9; N, 12.2. Found: C, 60.4; H, 4.2; N, 11.8%.
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4.3.4. Synthesis of [{Ru(tpy)(acac)}2(l-bcpea)] (5) 9,10-diethynylanthracene was first prepared: 9,10Bis[(trimethylsilyl)ethynyl]anthracene (55 mg, 0.15 mmol, 1 equiv.) was solubilized in the mixture of methanol/ diethylether (2:1, 12 ml) previously degassed with argon. To the obtained yellow solution was added a solution of potassium hydroxide in water (1.0 ml, 0.71 M). The mixture was stirred at 40 C under argon for 2.5 h and evaporated to dryness. The orange residue was dissolved in dry THF and used without any purification in the Sonogashira coupling reaction. [Ru(tpy)(acac)(Ipcyd)] (100 mg, 0.148 mmol), CuI (6.0 mg, 21 mol%) and Pd(PPh3)4 (11.1 mg, 6.5 mol%) were placed in the cosolvent DMF/piperidine (4:1, 5 ml) previously degassed with argon. The freshly prepared solution of 9,10-diethynylanthracene in THF was added and the initially blue-green solution turned instantly purple. The reaction mixture was stirred at room temperature for 3 h and then evaporated to dryness. The resulting purple solid was dissolved in dichloromethane and purified by column chromatography (weakly acidic alumina, solvent: dichloromethane, eluent: dichloromethane/ethanol 99:1 then 98:2). The second band (purple) was collected and then evaporated to dryness to give a dark purple powder of 5 (34 mg, 35%). 1H NMR (d6-DMSO, d = 2.50): 8.52–8.69 (16H, m); 8.10 (4H, dt, 7.7 and 1.6 Hz); 7.79 (2H, t, 8.0 Hz); 7.69–7.78 (8H, m); 7.24 (4H, d, 8.6 Hz); 6.03 (4H, d, 8.6 Hz); 5.35 (2H, s); 2.43 (6H, s); 1.30 (6H, s). IR m/cm1 2168s (NCN). ES mass spectrum (CH3CN) m/z: 1325 [M + H]+; 892 [[Ru(tpy)(acac)(L 0 H)] + H]+, 663 [M + 2H]2+. Anal. Calc. for C72H52N10O4Ru2(EtOH)(H2O)1,5: C, 63.6; H, 4.4; N, 10.0. Found: C, 64.0; H, 4.3; N, 9.6%.
4.4. Synthesis of ligands 4.4.1. Synthesis of hmbpcydH To a solution of IpcydH (1.00 g, 4.10 mmol), Pd(PPh3)4 (200 mg, 4 mol%) and CuI (160 mg, 20 mol%) in the previously degassed DMF/piperidine cosolvent (5:1, 30 ml) was added 2-methylbut-3-yn-2-ol (2.0 ml, 5 equivalents) under argon. The mixture was stirred for 1.5 h at room temperature and then evaporated to dryness. The remaining solid was purified by column chromatography (silica gel, solvent: dichloromethane, eluent: dichloromethane then dichloromethane/ethanol 98:2). The third band (yellow) was collected, evaporated to dryness and recrystallized from a dichloromethane/cyclohexane mixture to give a pale yellow powder of 2 0 (495 mg, 60%). 1H NMR (CD2Cl2 d = 5.35): 7.43 (2H, d, 8.9 Hz); 6.99 (2H, d, 8.9 Hz); 1.60 (6H, s). NMR1H (d6-DMSO d = 2.50): 7.36 (2H, d, 8.5 Hz); 6.93 (2H, d, 8.5 Hz); 5.45 (1H, s large); 1.44 (6H, s). IR m/cm1 2227s (C„N). EI mass spectrum (MeOH) m/z: 200 [M]+, 185 [M–CH3]+. Anal. Calc. for
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C12H12N2O(CH2Cl2)0,03: C, 71.3; H, 6.0; N, 13.8. Found: C, 71.5; H, 6.0; N, 13.7%. 4.4.2. Synthesis of epcydH A solution of hmbpcydH (490 mg, 2.45 mmol) and potassium tert-butoxide (360 mg, 3.21 mmol, 1.3 equivalents) in dimethylformamide (30 ml) was heated at 60 C for 1 h. At this stage, more potassium tert-butoxide (120 mg, 1.07 mmol, 0.4 equivalents) was added and the solution was stirred further for 1 h at 60 C. The mixture was then evaporated to dryness and dissolved in a mixture of dichloromethane (100 ml) and acetic acid (5 ml). This solution was washed with water (3 · 30 ml), dried over MgSO4 and evaporated to dryness. The residue was further purified by column chromatography (silica gel, solvent: dichloromethane, eluent: dichloromethane/ethanol 99:1) and recrystallized from a dichloromethane/cyclohexane mixture to afford a yellowish powder of 3 0 (240 mg, 69%). 1H NMR (CD2Cl2 d = 5.35): 7.51 (2H, d, 8.7 Hz); 7.02 (2H, d, 8.7 Hz); 6.36 (1H, s large); 3.15 (1H, s).1H NMR (d6-DMSO d = 2.50): 7.46 (2H, d, 8.8 Hz); 6.95 (2H, d, 8.8 Hz); 4.11 (1H, s). IR m/cm1 2230s (C„N) and 2105w (C„C). EI mass spectrum (MeOH) m/z: 142 [M]+. Anal. Calc. for C9H6N2 (H2O)0,02: C, 75.8; H, 4.3; N, 19.7. Found: C, 75.4; H, 4.4; N, 20.2%. 4.4.3. Synthesis of bcpdaH2 Copper (I) chloride (42 mg, 0.42 mmol) was placed in a three-necked round bottom flask equipped with a stir bar and an adaptor connected to an oxygen source. Pyridine (10 ml) and 1,8-diazabicyclo[5.4.0]undec-7-ene (0.65 ml, 4.3 mmol) were added and the mixture was warmed to 40 C and vigorously stirred while bubbling oxygen. The solution turned dark green after 10 min and epcydH (300 mg, 2.11 mmol) was added. The mixture was stirred at 40 C with oxygen bubbling for 1 h and then evaporated to dryness. The greenish residue was purified by column chromatography (silica gel, solvent: dichloromethane, eluent: dichloromethane/ethanol 99:1 then 97:3) and recrystallized from a dichloromethane/cyclohexane mixture to afford a yellow powder of 4 0 (53 mg, 18%). 1H NMR (d6-acetone d = 2.05): 7.60 (4H, d, 8.8 Hz); 7.11 (4H, d, 8.8 Hz); 9.20 (2H, s large). IR m/cm1 2227s and 2241sh (C„N). EI mass spectrum (MeOH) m/z: 282 [M]+. Anal. Calc. for C18H10N4 (H2O)0,1: C, 76.1; H, 3.6; N, 19.7. Found: C, 76.1; H, 3.8; N, 19.7%. 4.4.4. Synthesis of bcpeaH2 To a solution of IpcydH (100 mg, 0.410 mmol), Pd(PPh3)4 (22 mg, 4.6 mol%) and CuI (24 mg, 31 mol%) in the previously degassed cosolvent dimethylformamide/piperidine (3:1, 4 ml) was added 9,10-bis(3-hydroxy3-methylbutynyl)anthracene (68 mg, 0.20 mmol, 0.48 equivalents) and potassium tert-butoxide (112 mg,
1.06 mmol, 2.6 equivalents). After stirring for 1 h at 60 C, the reaction mixture initially yellow turned violet. At this stage, evaporation of the solution gave a solid, which was purified by column chromatography (silica gel, solvent: dichloromethane, eluent: dichloromethane/ ethanol 98:2 then 96:4) to yield a red powder of 5 0 (65 mg, 71%). 1H NMR (d6-acetone d = 2.05): 8.75 (4H, dd, 6.7 and 3.3 Hz); 7.89 (4H, d, 8.8 Hz); 7.74 (4H, dd, 6.7 and 3.3 Hz); 7.22 (4H, d, 8.8 Hz). IR m/cm1 2220s and 2234sh (CN). DCI mass spectrum (MeOH, NH3) m/z: 459 [M + H]+. Anal. Calc. for C32H18N4(H2O)0,6: C, 81.9; H, 4.1; N, 11.9. Found: C, 81.9; H, 4.1; N, 11.8%. 4.4.5. Synthesis of the tetraphenylarsonium salt of Ipcyd, [As(Ph)4][Ipcyd] IpcydH (200 mg, 0.820 mmol) was placed in a 2.0 M sodium hydroxide aqueous solution (10 ml) and the mixture was degassed and stirred under argon until complete dissolution. [As(Ph)4]Cl Æ H2O (400 mg, 0.955 mmol, 1.16 equivalents) was dissolved in a previously degassed 2.0 M sodium hydroxide aqueous solution (10 ml) and the resulting solution was transferred under argon to the basic solution of the ligand. The mixture was stirred for 0.5 h at room temperature and then the white precipitate was filtered, washed with water and vacuum dried to yield a white powder of the desired product (402 mg, 78%). 1H NMR (CD2Cl2 d = 5.35): 7.90 (4H, tt, 7.5 and 1.3 Hz); 7.78 (8H, m); 7.63 (8H, d, 7.3 Hz); 7.14 (2H, d, 8.9 Hz); 6.55 (2H, d, 8.9 Hz). IR m/cm1 2094s (NCN). ES mass spectrum (MeOH) m/z: 243 [Ipcyd], 383 [As(Ph)4]+. Anal. Calc. for C31H24N2IAs (H2O)2: C, 56.2; H, 4.3; N, 4.2. Found: C, 56.4; H, 4.1; N, 4.2%. 4.4.6. Synthesis of the tetraphenylarsonium salt of hmbpcyd, [As(Ph)4][hmbpcyd] The procedure was the same as for the synthesis of [As(Ph)4][Ipcyd] and a yellowish powder was obtained (65%). 1H NMR (CD2Cl2 d = 5.35): 7.90 (4H, tt, 7.4 and 1.3 Hz); 7.78 (8H, m); 7.63 (8H, d, 7.3 Hz); 6.98 (2H, d, 8.7 Hz); 6.65 (2H, d, 8.7 Hz); 1.56 (6H, s). IR m/cm1 2104s (NCN). ES mass spectrum (MeOH) m/z: 199 [hmbpcyd], 383 [As(Ph)4]+. Anal. Calc. for C36H31N2OAs (H2O)0,2: C, 73.7; H, 5.4; N, 4.8. Found: C, 73.6; H, 5.3; N, 4.8%. 4.4.7. Synthesis of the tetraphenylarsonium salt of epcyd, [As(Ph)4][epcyd] The procedure is identical to the synthesis of [As(Ph)4][Ipcyd] and a yellowish powder was obtained (69%). 1H NMR (CD2Cl2 d = 5.35): 7.90 (4H, tt, 7.4 and 1.3 Hz); 7.78 (8H, m); 7.63 (8H, d, 7.3 Hz); 7.07 (2H, d, 8.7 Hz); 6.66 (2H, d, 8.7 Hz); 2.95 (1H, s). IR m/cm1 2090s (NCN). ES mass spectrum (MeOH) m/z: 141 [epcyd], 383 [As(Ph)4]+. Anal. Calc. for C33H25
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N2As (H2O)0,4: C, 74.5; H, 4.9; N, 5.3. Found: C, 74.6; H, 4.7; N, 5.3%. 4.4.8. Synthesis of the tetraphenylarsonium salt of bcpda2, [As(Ph)4]2 [bcpda] The procedure was the same as for the synthesis of [As(Ph)4][Ipcyd] except that 2.4 equivalents of [As(Ph)4]Cl Æ H2O were used. A yellow powder was obtained (75%). 1H NMR (CD2Cl2 d = 5.35): 7.89 (8H, tt, 7.5 and 1.3 Hz); 7.77 (16H, m); 7.63 (16H, d, 7.2 Hz); 6.99 (4H, d, 8.8 Hz); 6.64 (4H, d, 8.8 Hz). IR m/cm1 2114s (NCN). ES mass spectrum (MeOH) m/z: 281 [LH], 383 [As(Ph)4]+. FAB mass spectrum (DMF) it m/z: 663 [L2, As(Ph)4+], 383 [As(Ph)4]+. Anal. Calc. for C66H48N4As2(H2O)3: C, 72.0; H, 4.9; N, 5.1. Found: C, 72.0; H, 4.8; N, 5.2%. 4.4.9. Synthesis of the tetraphenylarsonium salt of bcpea2, [As(Ph)4]2[bcpea] The procedure was similar to the synthesis of [As(Ph)4]2[bcpda] except that a mixture of 2.0 M NaOH aqueous solution and MeOH was used (5:1). A violet powder was obtained (78%). 1H NMR (CD2Cl2 d = 5.35): 8.65 (4H, dd, 6.5 and 3.3 Hz); 7.85 (8H, tt, 7.5 and 1.3 Hz); 7.72 (16H, m); 7.57 (4H, dd, 6.5 and 3.3 Hz); 7.55 (16H, d, 7.2 Hz); 7.38 (4H, d, 8.7 Hz); 6.84 (4H, d, 8.7 Hz). IR m/cm1 2099s and 2177s (NCN). ES mass spectrum (MeOH) m/z: 228 [L]2, 457 [LH], 383 [As(Ph)4]+. Anal. Calc. for C80H56N4As2(H2O)1,4: C, 77.0; H, 4.7; N, 4.5. Found: C, 76.8; H, 4.5; N, 4.3%. 4.5. Crystal structure determination of [Ru(tpy)(acac)(hmbpcyd)] (2) Dark blue needles were grown by slow evaporation of a mixture of an ethanol/water solution of the complex. The diffraction intensities were collected on a Nonius Kappa CCD diffractometer at room temperature, using graphite monochromated Mo Ka radiation ˚ ) at a detector distance of 4 cm. The crys(k = 0.71073 A tallographic cell was found by using EVAL-CCD [34]. The structure was solved using DIRDIFF [35] and refined in the maXus software package [36]. Absorption corrections were performed using SORTAV program Blessing 1995. The refinement was performed anisotropically for all the non-hydrogen atoms of the complex except for the oxygen of the water molecule. The hydrogen atoms were localized by difference Fourier ˚ , then their synthesis, recalculated and fixed at 0.97 A contributions were introduced in the calculations but not refined. 1526 reflections [I > 3r(I)] were used for the 375 parameters and the R value dropped to 0.040. The full experimental details, atomic parameters and the complete listing of bond lengths and angles are available as supplementary data.
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Acknowledgments The authors thank CNRS and MENRS (M.F.) for financial support, Yannick Coppel (Laboratoire de Chimie de Coordination LCC/CNRS) for the 13C NMR spectra, Christine Viala (CEMES) for technical assistance and Christophe Coudret (CEMES) for helpful advice.
Appendix A. Supplementary data 1
H and 13C NMR spectral data for [Ru(tpy)(acac)(hmbpcyd)] 2 in d6-DMSO (Table S1). 1H and 13 C NMR spectral data for [Ru(tpy)(acac)(epcyd)] (3) in d6-DMSO (Table S2). 1H NMR spectra of 2 in d6-DMSO at 293 K (Figure S1). Cyclic voltammogram of 2 in DMF containing 0.1 M TBAH in the range 1.8:+0.8 V (Figure S2). Differential pulse voltammogram of 2 in DMF containing 0.1 M TBAH in the range 1.8:+1.5 V (Figure S3). UV–Vis spectra of the tetraphenylarsonium salts of the phenylcyanamide derivative ligands in DMF (Figure S4). Comparison of the electronic absorption spectra of complex 4 and [AsPh4]2[bcpda] in DMF (Figure S5). Comparison of the electronic absorption spectra of complex 5 and [AsPh4]2[bcpea] in DMF (Figure 6). Stepwise spectroelectrochemical oxidation and reduction of 4 and 42+in DMF containing 0.1 M TBAH (Figures S7 and S8). X-ray crystallographic files in CIF format for the structure determination of 2, CCDC 235561. These data can be obtained free of charge via www.ccdc. cam.ac.uk/data_request/cif, by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.’’ Supplementary data associated with this article can be found, in the online version, at doi:10.1016/ j.ica.2005.01.004.
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