Copper(II) complexes with unsymmetrical pentadentate ed3a-type diamino-tricarboxylate ligands. Crystal structures, configurational analysis and DFT study of complexes

Inorganica Chimica Acta 360 (2007) 2420–2431 www.elsevier.com/locate/ica

Copper(II) complexes with unsymmetrical pentadentate ed3a-type diamino-tricarboxylate ligands. Crystal structures, configurational analysis and DFT study of complexes Zoran D. Matovic´ b

a,*

, Auke Meetsma b, Vesna D. Miletic´ a, Petra J. van Koningsbruggen

b

a Department of Chemistry, Faculty of Science, University of Kragujevac, Kragujevac, SRB-34000, Serbia and Montenegro Stratingh Institute for Chemistry and Chemical Engineering, University of Groningen, Nijenborgh 4, NL-9747 AG Groningen, The Netherlands

Received 22 November 2006; received in revised form 5 December 2006; accepted 5 December 2006 Available online 15 December 2006

Abstract The O–O–N–N–O-type pentadentate ligands H3ed3a, H3pd3a and H3pd3p (H3ed3a stands ethylenediamine-N,N,N 0 -triacetic acid; H3pd3a stands 1,3-propanediamine-N,N,N 0 -triacetic acid and H3pd3p stands 1,3-propanediamine-N,N,N 0 -tri-3-propionic acid) and the corresponding novel octahedral or square-planar/trigonal-bipyramidal copper(II) complexes have been prepared and characterized. H3ed3a, H3pd3a and H3pd3p ligands coordinate to copper(II) ion via five donor atoms (three deprotonated carboxylate atoms and two amine nitrogens) affording octahedral in case of ed3a3 and intermediate square-pyramidal/trigonal-bipyramidal structure in case of pd3a3 and pd3p3. A six coordinate, octahedral geometry has been established crystallographically for the [Mg(H2O)6][Cu(ed3a) (H2O)]2 Æ 2H2O complex and five coordinate square-pyramidal for the [Mg(H2O)5Cu(pd3a)][Cu(pd3a)] Æ 2H2O. Structural data correlating similar chelate Cu(II) complexes have been used for the better understanding the pathway: octahedral ! square-pyramidal M trigonal- bipyramid geometry. An extensive configuration analysis is discussed in relation to information obtained for similar complexes. The infra-red and electronic absorption spectra of the complexes are discussed in comparison with related complexes of known geometries. Molecular mechanics and density functional theory (DFT) programs have been used to model the most stable geometric isomer yielding, at the same time, significant structural data. The results from density functional studies have been compared with X-ray data.  2006 Elsevier B.V. All rights reserved. Keywords: Copper(II) complexes; Aminopolycarboxylates; Crystal structure; DFT; Pentadentates

1. Introduction Structural variations of the chelate edta-type framework involve increasing the size or rigidity of the chains, or omitting one or more of the carboxylate arms. Isomerism is possible for complexes of hexadentate edta-type ligands where the carboxylate arms are replaced so as to form nonequivalent chelate rings [1,2]. In many cases where the number of donor atoms bound to the metal ion is less than six, the pentadentate or tetradentate ligands admit the possibility of further isomerism. A linear flexible edda-type (ethylene-

*

Corresponding author. Tel.: +381 34 33 62 23; fax: +381 34 33 50 40. E-mail address: [email protected] (Z.D. Matovic´).

0020-1693/$ - see front matter  2006 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2006.12.015

diamine-N,N 0 -diacetate) ligand can occupy four coordination sites with three geometric isomers possible: trans, s-cis and uns-cis where the uns-cis is the predominant geometry of known octahedral complexes [3,4]. In general, when edta or ed3a (ethylenediamine-N,N,N 0 -triacetate) is pentadentate three possible geometric isomers are expected (Fig. 1a). When two monodentate ligands are present in a molecule the number of possible isomers extends to eight. The isomers are assigned as cis-equatorial, trans-equatorial and cis-polar. The studies of [M(ed3a-type)X] complexes (M = Co(III), Cr(III) and X = monodentate ligand) in last decades are mostly limited to the cis-equatorial configuration and this structure has been verified crystallographically [5–8]. Contrary to this, most complexes of Cu(II) with edda- or ed3a-type of ligands appear in a

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Fig. 1. Geometrical isomerism of six-coordinate [M(ed3a-type)Xn] complexes: (a) n = 1, (b) n = 2.

square-pyramidal (SPy) geometry. We have already reported three square-pyramidal [Cu(edda-type)(H2O)] complexes containing in-plane linear tetradentate ligands: 1,3-pdda (1,3-propanediamine-N,N 0 -diacetate ion), eddp (ethylenediamine-N,N-di-3-propionate ion), or 1,3-pddp (1,3-propanediamine-N,N 0 -di-3-propionate ion), and a water molecule in the axial position [4] where the factors determining their geometry have been discussed. The absence of different geometrical isomers (symmetrical-cis, unsymmetrical-cis and trans) [1], already found in complexes with other metal ions [3,4], we attributed to the d9-electron configuration of the copper(II) ion and consequently to the presence of a Jahn–Teller effect [9]. However, the formation of a particular geometry depends on several other factors such as: in-plane ligand field strength (LFS), the structure of a ligand and the size of chelate rings. Recently, we described a square-planar diamido or amido carboxylate complexes containing tetradentate mda or obap ligands (mda stands for the malamidoN,N 0 -diacetato ion and H3obap = oxamido-N-aminopropyl-N 0 -benzoic acid) [10,11]. By increasing the size of the chelate rings, the complexity of the ring conformations increases and the magnitude of interactions between adjacent ligands increases [12]. These interactions account for the distribution of isomers in the metal–ligand complexes. Factors determin-

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ing the geometry in M(O–O–N–N–O-type) and related complexes: the d-electron configuration and size of the central metal ion [13–15] can also be considered for the complexes in question. The multidentate ed3p ligand (ethylenediamine-N,N,N 0 -tri-3-propionate ion) and its analogs form with Cr(III) ion octahedral complexes [Cr(ed3p-type)(H2O)] [16,17]. However, this ligand forms square-pyramidal (SPy) Cu(II) complexes and this geometry of the complex anion was established in the crystal structure of Ba[Cu(ed3p)](ClO4) Æ 5H2O [18]. We believe that this is the first example of Cu(II) complexes with carboxylate-unsymmetric pentadentate ed3a-type ligands for which the structural story was encircled by the X-ray analysis. Pentadentate ed3a-type ligands may contain equal or mixed carboxylate arms and can be symmetrical or unsymmetrical. In the present study, the ed3a, pd3a and pd3p ligands (pd3a and pd3p stand for 1,3-propanediamineN,N,N 0 -triacetate and 1,3-propanediamine-N,N,N 0 -di-3propionate ions, respectively) have been used in an attempt to prepare the corresponding square-pyramidal Cu(II) complexes. We had success in case of [Mg(H2O)5Cu(1,3pd3a)][Cu(1,3-pd3a)] Æ 2H2O and Ba[Cu(pd3p)]2 Æ 8H2O complexes in adopting SPy geometry but [Mg(H2O)6][Cu(ed3a)(H2O)]2 Æ 2H2O complex was found in an octahedral surrounding. The geometries of [Mg(H2O)6][Cu(ed3a)(H2O)]2 Æ 2H2O and [Mg(H2O)5Cu(1,3-pd3a)][Cu(1,3-pd3a)] Æ 2H2O have been verified by X-ray analysis. The structural parameters and spectral data of the actual complexes and those reported for related complexes are compared and discussed in relation to their stereochemistry. Here we report the preparation and characterization of H3ed3a, H3pd3p and H3pd3a ligands and corresponding octahedral [Mg(H2O)6][Cu(ed3a)(H2O)]2 Æ 2H2O and square-pyramidal [Mg(H2O)5Cu(1,3-pd3a)][Cu(1,3-pd3a)] Æ 2H2O and Ba[Cu(pd3p)]2 Æ 8H2O complexes. The complexes contain fully deprotonated pentadentate ligands which are capable of forming only five-membered (H3ed3a) or six-membered (H3pd3p) or mixed five- and six-membered backbone or acetate ring (H3pd3a). The IR and electronic spectra of the investigated complexes are discussed in relation to their geometry. In addition, molecular mechanics and density functional theory (DFT) methods have been used to model the most stable geometric isomer yielding, at the same time, significant structural data. The results from DFT studies have been compared with X-ray data. 2. Experimental 2.1. Chemicals Reagent grade, commercially available, chemicals were used without further purification. Ethanediamine, 1,3propanediamine, 3-chloropropionic and chloroacetic acids were purchased from Fluka and used as supplied.

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2.2. Measurements C, H, N analyses were performed at the Microanalytical laboratory, Faculty of Chemistry, University of Belgrade, Serbia. IR spectra in the 400–4000 cm1 region were recorded on a Perkin–Elmer FTIR spectrophotometer Spectrumone, using the KBr pellets technique. Electronic absorption spectra were recorded on a Perkin–Elmer Lambda 35 spectrophotometer. For these measurements 1 · 103 M aqueous solutions of the complexes under investigation were used. Suitable blue-green-colored block-shaped crystals of (1) (see further text in experimental) were obtained by recrystallization from water. Blue colored crystals of (2) were obtained by recrystallization from a mixture of methanol and water. A crystal fragments of (1) and (2) with the dimensions of 0.33 · 0.22 · 0.19 mm and 0.11 · 0.08 · 0.035 mm, respectively, were mounted on top of a glass fiber and aligned on a Bruker KRYOFLEX SMART APEX CCD diffractometer (Platform with full three-circle goniometer). The crystals were cooled to 100(1) K. Intensity measurements were performed using graphite monochromated Mo Ka radiation from a sealed ceramic diffraction tube (SIEMENS). The final unit cells were obtained from the xyz centroids of 7502 for (1) and of 6641 reflections for (2) after integration. Intensity data were corrected for Lorentz and polarization effects, scale variation, for decay and absorption: a multi-scan absorption correction was applied, based on the intensities of symmetry-related reflections measured at different angular settings (SADABS) [19], and reduced to F 2o . The program suite SHELXTL was used for space groups determination (XPREP) [20]. The unit cell [21] was identified as monoclinic in both cases; the space group P21/c for both crystals was derived from the systematic extinctions. The structures were solved by Patterson methods and extension of the model was accomplished by direct methods applied to difference structure factors using the program DIRDIF [22]. The positional and anisotropic displacement parameters for the non-hydrogen atoms were refined. Final refinement on F2 carried out by full-matrix least-squares techniques. The final difference Fourier maps were essentially feature˚ 3 within 1.0 A ˚ less with two peaks of max. 1.24(13) e/A from Cu in crystal (1), but were neglected/rejected, being artefacts. The positional and anisotropic displacement parameters for the non-hydrogen atoms and isotropic displacement parameters for hydrogen atoms were refined on F2 with full-matrix least-squares procedures. Neutral atom scattering factors and anomalous dispersion corrections were taken from International Tables for Crystallography [23] All refinement calculations and graphics were performed on a HP XW6200 (Intel XEON 3.2 GHz)/ Debian-Linux computer at the University of Groningen with the program packages SHELXL [24] (least-square refinements), a locally modified version of the program

[25] (preparation of illustrations) and PLATON [26] package (checking the final results for missed symmetry with the MISSYM option, solvent accessible voids with the SOLV option, calculation of geometric data and the ORTEP [26] illustrations). Crystal data, numerical details and refinement are given in Table 1. PLUTO

2.3. Preparation of calcium salt of ethylenediamine-N,N,N 0 triacetic acid, Ca3(ed3a)2 Æ 12H2O Monochloroacetic acid (56.7 g; 600 mmol) was dissolved in 180 ml of demineralized water and 29.8 g (400 mmol) calcium hydroxide was added to the solution. The pH rose from 1.0 to 11.7. Subsequently, 12 g (200 mmol) of ethylenediamine was added within 10 min. The temperature was kept at about 50 C without additional heating. After 1 h the temperature was increased to 70 C and the resulting mixture was left for additional 5.5 h. During the entire reaction, the pH was kept constant at 7.5–8.0 by the addition of calcium hydroxide. At the end of the reaction, a total of 41.4 g (560 mmol) of calcium hydroxide had been added. The reaction mixture was filtered warm over a glass filter to remove excess of calcium hydroxide. The filtrate was allowed to cool to room temperature. After one night a precipitate had formed. Yield: 44.7 g (87%) calculated on the amount of ethylenediamine initially applied. Anal. Calc. for C16H46N4O24Ca3; Mw = 798.78: C, 24.06; H, 5.80; N, 7.01. Found:C, 23.87; H, 5.50; N, 6.72%. IR data for m(N–H): 3333 cm1, mas(COO) = 1617 cm1, 1583 cm1, ms(COO) = 1442 cm1. 2.4. Preparation of hexaaquomagnesiumbis[(ethylenediamine-N,N,N 0 -triacetato)aquocuprate(II)] dihydrate, [Mg(H2O)6][Cu(ed3a)(H2O)]2 Æ 2H2O (1) Ca3(ed3a)2 Æ 12H2O (5.99 g, 7.5 mmol) was dissolved in 40 ml of water and solution of 1.80 g (45 mmol) NaOH in 5 ml of water was added. The deposited Ca(OH)2 was separated by filtration under vacuum and in filtrate was added the solution of 2.56 g (15 mmol) CuCl2 Æ 2H2O in 15 ml of water. The resulting mixture was stirred at 65 C for 1 h. The blue suspension was then filtered and desalted by passage through a G-10 Sephadex column, with distilled water as the eluent. The resulting blue solution was poured into a 4 · 40 cm column containing Dowex 1-X8 (200–400 mesh) anionexchange resin in the Cl form. The column was then washed with water and eluted with 0.1 M solution of MgCl2. Two bands were obtained (ca. 1:10). The second eluate was evaporated to 10 ml and desalted by passage through a G-10 Sephadex column, with distilled water as the eluent. After that the eluate was concentrated to a volume of 3 ml and left to crystallize from ethanol during several days. Yield: 1.0 g. Melting point: 240 C. Anal. Calc. for C16H42N4O22Cu2Mg; Mw = 793.92: C, 24.21; H, 5.33; N, 7.06. Found: C, 24.12; H, 5.62; N, 7.06%. UV–Vis data: kmax = 14 327 cm1 (e = 88.30 mol1 dm3cm1). IR data: m(NH) = 3372 cm1, mas(COO) = 1603 cm1, ms(COO) = 1434, 1408, 1363 cm1.

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Table 1 Crystal data for complexes [Mg(H2O)6][Cu(ed3a)(H2O)]2 Æ 2H2O (1) and [Mg(H2O)5Cu(1,3-pd3a)][Cu(1,3-pd3a)] Æ 2H2O (2) Empirical formula Formula weight (g mol1) Crystal system Space group, no. ˚) a (A ˚) b (A ˚) c (A b () ˚ 3) V (A H range unit cell: minimum–maximum, deg; reflections Z qcalc (g cm3) F(000), electrons l(Mo Ka) (cm1) ˚) Radiation type; k (A Temperature (K) h Range; minimum, maximum () Index ranges Total data, unique data Data with criterion: (Fo P 4r(Fo)) Number of reflections Number of refined parameters P P wRðF 2 Þ ¼ ½ ½wðF 2o  F 2c Þ2 = ½wðF 2o Þ2 1=2 Weighting P scheme: a, b P RðF Þ ¼ ðjjF o j  jF c jjÞ= jF o j ˚ 3) Difference Fourier map (e/A a

1

2

C16H42N4O22Cu2Mg 793.92 monoclinic P21/c, 14 14.482(1) 11.199(1) 9.0185(8) 94.852(1) 1457.4(2) 2.25–19.80; 7502 2 1.809 824 15.82 Mo Ka, 0.71073 100(1) 2.82, 28.28 h: 19 ! 19; k: 14 ! 14; l: 10 ! 12 12 861, 3572 3336 3572 289 0.0952 0.0657, 0.5510a 0.0349 1.06, 1.24(13)

C18H40N4O19Cu2Mg 767.93 monoclinic P21/c, 14 19.717(5) 11.036(3) 13.555(3) 106.148(4) 2833.2(12) 2.83–27.50; 6641 4 1.800 1592 16.17 Mo Ka, 0.71073 100(1) 2.82, 24.41 h: 22 ! 22; k: 12 ! 12; l: 15 ! 15 17784, 4657 3248 4657 455 0.1865 0.0, 15.1450 0.0786 1.2, 0.9(2)

w ¼ 1=½r2 ðF 2o Þ þ ðaP Þ2 þ bP  and P ¼ ½maxðF 2o ; 0Þ þ 2F 2c =3.

2.5. Preparation of pentaaquomagnesiumbis[(propanediamine-N,N,N 0 -triacetato)cuprate(II)] dihydrate, [Mg(H2O)5Cu(pd3a)][Cu(pd3a)] Æ 2H2O (2) from condensation mixture containing 1,3-propanediamineN,N,N 0 -triacetic acid Monochloroacetic acid (11.5 g, 120 mmol) was dissolved in 42 ml of demineralized water and 4.7 g (84 mmol) calcium oxide was added to the solution. The pH rose from 1.0 to 11.2. Subsequently, 3.11 g (42 mmol) of 1,3-propanediamine was added in 10 min. The temperature was kept at about 50 C without additional heating. After 1 h the temperature was increased to 70 C and the resulting mixture was left for additional 5.5 h. During the entire reaction, the pH was kept constant at 7.5–8.0 by the addition of calcium oxide. At the end of the reaction, a total of 1.9 g (34 mmol) of calcium oxide had been added. The reaction mixture was filtered warm over a glass filter to remove excess of calcium hydroxide. The reaction mixture (volume 50 ml) contains pd3a (50%), pdta (18%) i pdda (23%). In 25 ml of reaction mixture the solution of 2.52 g (63 mmol) NaOH in 5 ml of water was added. The deposited calcium hydroxide was removed by filtration. To this filtrate was then added the solution obtained by dissolving 3.58 g (21 mmol) of CuCl2 Æ 2H2O in 8 ml of water. Reaction mixture was stirred at 65 C for 1 h and after that was filtered. The obtained filtrate was then desalted by

passing it through a G-10 Sephadex column while eluting with water, and then poured into a 50 · 60 cm column containing Dowex 1-X8 (200–400 mesh) anion exchange resin in the Cl form. The column was washed with water and after that with 0.1 M MgCl2 solution (ca. 0.5 ml/min). Two bands with 1 charge appeared on the column. The obtained eluates were desalted and reduced to 10 ml and then allowed to stand in a refrigerator for several days. Blue crystals from the first eluate represent complex (2). Yield: 1.4 g. Melting point: 243 C Anal. Calc. for C18H40N4O19Cu2Mg; Mw = 767.93: C, 28,15; H, 5,25; N, 7,30. Found: C, 28.31; H, 5.52; N, 7.22%. UV–Vis data: kmax = 15221 cm1 (e = 60.33 mol1 dm3 cm1). IR data for m(NH) = 3240 cm1, mas(COO) = 1607 cm1, ms(COO) = 1432, 1392 cm1.

2.6. Preparation of barium(propanediamine-N,N,N 0 -tri-3propionato)cuprate(II) octahydrate, Ba[Cu(pd3p)]2 Æ 8H2O (3) from condensation mixture containing 1,3-propanediamine-N,N,N 0 -3-tripropionic acid 21.7 g (200 mmol) 3-chloropropionic acid was dissolved in 30 ml of water and cooled in an ice bath. A cooled solution of NaOH (8.0 g, 0.20 mol) in 15 ml of water was added dropwise, the rate of addition being adjusted so that the temperature remained below 15 C. 1,3-propanediamine (3 g, 40 mmol) was added to this solution and the reaction

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mixture was heated at 70 C for 4 h. During this process an additional amount of NaOH (8.0 g, 200 mmol in 20 ml of water) was added dropwise to keep the pH in the range 7– 8. The volume of the resulting solution was 70 ml. The product represents a mixture of propanediamine-polycarboxylate ligands. A solution of 6.8 g (40 mmol) CuCl2 Æ 2H2O in 30 ml of water was added to the reaction of mixture. After the pH of the mixture was adjusted to approximately 7 by gradual addition of solution of NaOH the blue solution was then heated at 65 C with stirring for 1 h (the volume of the solution was maintained by periodic addition of hot water). The suspension was then filtered and desalted by passage through a G-10 Sephadex column, with distilled water as the eluent. The resulting blue solution was poured into a 5 · 60 cm column containing Dowex 1-X8 (200–400 mesh) anionexchange resin in the Cl form. The column was then washed with water and eluted with 0.1 M solution of BaCl2. Two bands were obtained. The eluates were evaporated to 10 ml and desalted by passage through a G-10 Sephadex column, with distilled water as the eluent. After that the eluates was concentrated to a volume of 3 ml and crystallized from ethanol for several days. Eluate of the first band was Ba[Cu(1,3-pdadp)]2, and the second was Ba[Cu(1,3-pd3p)]2. Yield: 1.55 g of Ba[Cu(1,3-pd3p)]2 (the second band). Melting point: 251 C. Anal. Calc. for C24H54N4O20Cu2Ba Æ 8H2O, Mw = 983.12: C, 29.32; H, 5.54; N, 5.70. Found: C, 29.16; H, 5.98; N, 5.65%. UV–Vis data: kmax = 14144 cm1 (e = 30 mol1 dm3 cm1). IR: m(N–H) = 3411 cm1, mas(COO) = 1583 cm1, ms(COO) = 1426, 1388 cm1.

2.7. Computational method The standard DFT method of quantum chemistry (Amsterdam Density Functional – ADF2006.01) [27–29] with Vosko–Wilk–Nussair (VWN) parameterization for the local density approximation (LDA) and Becke exchange and Perdew correlation gradient corrections has been used in order to find the optimal geometries of trigonal-bipyramidal and square-planar Cu(II) complexes. No symmetry restrictions were applied. Cu(II) systems were treated within the unrestricted formalism. The different geometries of the individual chelate systems (starting from either experimental structures (X-ray determined) or MM+ preoptimized) were optimized until the maximum and the root-mean-squared gradients were below 0.01 and 0.007 ˚ and the maximum and rootmean-squared Hartree/A ˚ , respecchanges in geometry were below 0.01 and 0.007 A tively. For all atoms, Slater-type orbital (STO) basis sets of triple-n quality with polarization functions (TZP type) from the ADF library have been used. The inner shells were represented by frozen core approximation (1s for C, N, O and 1s-2p for Cu were kept frozen). The subsequent frequency calculations at the same level verified the optimized structures to be ground states without imaginary frequencies.

3. Results and discussion 3.1. Preparation of unsymmetrical diaminotricarboxylate ligands and corresponding Cu(II) complexes and their characterization Suprisingly, the wealth of aminopolycarboxylate ligands and corresponding metal (mostly Fe) complexes have been prepared by the chemists from world-wide well known photo-corporations (Fuji, Conica, etc.) with only one goal in mind: to prepare better substances for processing silver halide photographic light-sensitive material. However, from the coordination chemistry point of view, these investigations, published mainly as patents, are very poor but some preparative methods for chelate ligands might be used. In the past, EDTA-type chelates were prepared. Such chelates have been prepared following several methods: by the condensation method starting from neutralized a- or b-monohalogencarboxylic acid and corresponding diamine; by condensation of acrylic acid and diamine (in case you wish to obtain chelates with propionic arms); by condensation of dihalogen derivatives of diamine with diverse amino-acids. In our case the chelate pentadentate O–O–N– N–O ligands: H3ed3a, H3pd3a and H3pd3p have been prepared starting from neutralized monochloroacetic acid and ethanediamine/1,3-propanediamine (in case of H3ed3a/ H3pd3a) or b-chloropropionic acid and 1,3-propanediamine in case of H3pd3p. Just in case of H3ed3a we were successful in isolating the calcium salt of the acid and consequent characterization of the ligand has been done (see Section 2). Two further acids H3pd3a and H3pd3p have been prepared as a condensation mixture and as such used for complexation of Cu(II). It is confirmed by the investigations of acids in solution that these exist in zwitter ionic forms [2]. All the complexes have been prepared by complexing chloride salt of Cu(II) with neutralized chelate acids under conditions given in experimental. The mixture of complex species has been separated chromatographically using dowex resin. Different cations have been introduced into molecule using either different metal chlorides as chromatographic eluent or by ion exchange chromatography. Finally, we isolated: blue-green colored [Mg(H2O)6][Cu(ed3a)(H2O)]2 Æ 2H2O, blue colored [Mg(H2O)5Cu(pd3a)][Cu(pd3a)] Æ 2H2O and blue colored Ba[Cu(1,3pd3p)]2 Æ 8H2O complexes. The complexes were characterized by microanalysis and spectroscopic techniques (IR, UV–Vis, UV-reflectance). The structural and spectral data of similar complexes (Cu-ed3p, Cu-edtp) are compared and discussed in relation to their geometry. Contrary to our expectation, instead of SPy geometry the octahedral geometry of the complex anion, [Cu(ed3a)(H2O)], has been revealed in the crystal structure of the corresponding Mg(II) salts. In case of Co(III) and Cr(III) [1,2], the favorable cis-equatorial geometric configuration has been found and such framework also encircled the Cu(II) ion. Our parallel structural study on

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chelate ed3a-type complexes with Ni(II) indicated that the ed3a3 anion favors solely the cis-equatorial geometric isomer [30]. Furthermore, the crystallographic [M(ed3a)(H2O)] units [M = Cu(II), Ni(II)] appeared to be isomorphous adopting M-ed3a cis-equatorial geometry in both cases. This is quite uncommon when copper is in question. Usually, copper(II) is the main factor that governs the final geometry (particularly due to Jahn–Teller effects) as one can see in case of other diamino-polycarboxylic chelates: plane coordination of 1,3-pdda and eddp (1,3-pdda = 1,3-propanediamine-N,N 0 -diacetate; eddp = ethanediamine-N,N 0 -diacetate) instead of uns-cis geometry [4]; SPy coordination of edtp4 (ethanediamine-N,N,N 0 ,N 0 -tetra-3propionate) instead of octahedral geometry [31]; trans(O6) coordination of 1,3-pddadp (1,3-propanediamine-N,N 0 diacetate-N,N 0 -di-3- propionate) instead of favorable trans(O5) geometry [2]. It seems that magic copper is finally conquered by the ed3a molecule. The cis-equatorial geometry has been verified crystallographically for [Mg(H2O)6][Cu(ed3a)(H2O)]2 Æ 2H2O. The other two complex species, [Mg(H2O)5Cu(pd3a)][Cu(pd3a)] Æ 2H2O and Ba[Cu(pd3p)]2 Æ 8H2O, adopt square-pyramidal geometry as expected when copper(II) is in question [18,31]. The Spy geometry of (2) has been verified by an X-ray analysis. The spectroscopy techniques and DFT modelling indicated that Ba[Cu(pd3p)]2 Æ 8H2O adopts Spy geometry as the most probable one. For structural prediction we model all the complexes by DFT quantum mechanics using for that purpose ADF2006.01 program. ADF2006.01 has been used to optimize different geometries and consequently to give the answer which one is the most stable. Further use is found in determining the main energetic contribution to the formation of the most stable isomer. 3.2. Description of the crystal structures of (1) and (2) 3.2.1. [Mg(H2O)6][Cu(ed3a)(H2O)]2 Æ 2H2O (1) An X-ray diffraction study has been carried out on complex (1) and the experimental details are reported in Table 1. The adopted atom-numbering scheme of the atoms and the configuration of the cation- and anion-moiety along with the packing of the molecules in the unit cell are shown in Fig. 2. Each asymmetric unit contains one formula unit, consisting of three moieties: an anionic [Cu(ed3a)(H2O)] complex, a half cationic hydrated Mg complex and a solvate water molecule, the Mg(II) ion being located on the inversion center. Therefore, the monoclinic unit cell contains 10 units i.e. two cations, four anions and four water molecules. A search of the distances yielded intermolecular and intramolecular contacts shorter than the sum of the van der Waals radii [32] for the atoms. According to these results the moieties are linked by hydrogen bonds [32–35], forming an infinite two-dimensional network (Fig. 2b) along the base vectors [0 1 0] and [0 0 1]. The cis-equatorial [Cu(ed3a)(H2O)] entity contains a Cu(II) ion in a considerably distorted octahedral N2O4

Fig. 2. (a) ORTEP view of (1) with the scheme of atom numbering and (b) packing in the unit cell along c axis.

environment. The Jahn–Teller distortion for Cu(II) gives rise to an elongated or ‘‘compressed’’ octahedral geometry for [Cu(ed3a)(H2O)]. In the crystal structure (see Fig. 2a) the copper(II) ion coordinates five donor atoms from the ligand: three deprotonated carboxylic oxygens, two amine nitrogen atoms (secondary and tertiary), and a water mol˚ ecule. The distances are within the range 1.940 and 2.334 A (see Table 2) and as expected comparable with those obtained for related diamino ed3a-type complexes [18,31] except unusually long axial Cu–N12 distance ˚ ). The copper atom in (1) is slightly displaced (2.2222(15) A from the average plane defined by the donor atoms ˚ ). The cis angles at the copper(II) ion range (q = 0.0796 A from 84.9 to 94.4 and the trans angles from 155.6 to 174.4 showing large distorsion.

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Table 2 ˚ ) and bond angles () for complexes (1) and (2) with e.s.d.’s in parentheses Bond lengths (A Complex (1) Bond lengths Cu–O12 Cu–O14 Cu–O16 Cu–O17 Cu–N11 Cu–N12 Mg2–O21 Mg2–O22 Mg2–O23

Bond angles O12–Cu1–O14 O12–Cu1–O16 O12–Cu1–O17 O12–Cu1–N11 O12–Cu1–N12 O14–Cu1–O16 O14–Cu1–O17 O14–Cu1–N11 O14–Cu1–N12 O16–Cu1–O17 O16–Cu1–N11 O16–Cu1–N12 O17–Cu1–N11 O17–Cu1–N12 N11–Cu–1N12

Complex (2) unit 1 2.3341(12) 1.9400(12) 1.9799(12) 2.0004(14) 2.0790(14) 2.2222(15) 2.0170(15) 2.0164(14) 2.0931(15)

95.88(5) 89.30(5) 90.73(5) 75.51(5) 155.65(5) 174.42(5) 88.37(6) 84.91(5) 94.41(5) 93.67(6) 94.40(5) 80.01(5) 163.94(6) 111.60(6) 83.51(6)

Cu1–O11 Cu1–O13 Cu1–O15 Cu1–N11 Cu1–N12 Mg1–O14 Mg1–O17 Mg1–O18 Mg1–O19 Mg1–O110 Mg1–O111 O11–Cu1–O13 O11–Cu1–O15 O11–Cu1–N11 O11–Cu1–N12 O13–Cu1–O15 O13–Cu1–N11 O13–Cu1–N12 O15–Cu1–N11 O15–Cu1–N12 N11–Cu1–N12

The chelation rings are significantly different: while two five-membered acetate rings CuO14C16C15N11 and CuO16C18C17N12 (with puckering parameters q2 = ˚ , u2 = 314.9(6) and q2 = 0.1646(15) A ˚ , u2 = 0.1412(15) A 319.5(5), respectively) are nearly planar, the third acetato CuO12C14C13N11 ring (with puckering parameters ˚ , u2 = 339.2(2)) adopted an envelope q2 = 0.4310(13) A conformation. The backbone diamine ring (with puckering ˚ , u2 = 89.84(17)) has been parameters q2 = 0.4497(19) A found in twisted-envelope conformation. Let us return to the, for this type of compounds, quite ˚ ) and consequently unusually long Cu–N12 bond (2.334 A unusual complex configuration where two nitrogens do not belong to the equatorial plane. One may argue about this phenomenon from an electronic point of view (secondary versus tertiary amine) or steric or even conformational effects can be invoked for such a configurational layout of the ed3a around the copper ion. We would say that all of these effects have contributed in certain extent to create such an uncommon tetragonal complex where two nitrogens were not seen in the so-called equatorial plane. However, one cannot be so sure what kind of tetragonality to attribute to this complex. We can name it as tetragonally elongated unit along N12–Cu–O12 direction (as this is directions with lengthened Cu–O and Cu–N bonds) as stated above but at the same time this complex might be considered as a tetragonally compressed one neglecting the in-plane bond lengths difference D = longest(2.3341) 

Complex (2) unit 2 1.915(5) 2.137(6) 1.940(6) 2.048(8) 1.974(7) 2.034(7) 2.059(7) 2.038(7) 2.025(7) 2.071(7) 2.048(6) 100.5(2) 90.6(2) 84.1(3) 166.8(3) 101.4(2) 83.1(3) 92.5(2) 173.6(3) 84.5(2) 99.9(3)

Cu2–O21 Cu2–O23 Cu2–O25 Cu2–N21 Cu2–N22

O21–Cu2–O23 O21–Cu2–O25 O21–Cu2–N21 O21–Cu2–N22 O23–Cu2–O25 O23–Cu2–N21 O23–Cu2–N22 O25–Cu2–N21 O25–Cu2–N22 N21–Cu2–N22

2.234(6) 1.910(6) 1.914(6) 2.004(7) 1.978(8)

95.8(2) 115.1(2) 81.3(3) 93.2(3) 92.1(2) 86.5(3) 170.9(3) 163.6(3) 85.3(3) 93.6(3)

˚ . We can even neglect the lonshortest(2.004) = 0.3301 A ˚ and quite regular squaregest bond Cu–O12 of 2.3341 A pyramid might appear with low 17.5% trigonality (see configurational aspect of discussion Table 3). Let us say that the first choice is the right one, however, still the question about such displacement remains. Here we want to mention that [Cu(ed3a)(H2O)] is isomorphous with [Ni(ed3a)(H2O)] [30]. Furthermore, their similarity is so evident that it crosses to almost identity. We extracted coordinated ed3a ligands from these complexes and made up their overlay. Surprisingly, we obtained excellent fit with very good RMS error of 0.01243 (Fig. 3) and when overlayed Cu(ed3a) and Ni(ed3a) complexes RMS error was 0.0460. Disability of Cu(II) to attracts two N and two O chelate atoms into basal plane lies the least in different nature of nitrogens or electronic effects of copper. Again the major reason for this feature we should seek in extremely unfavourable presence of three five-membered rings in equatorial plane due to considerable strain effect. As a consequence cis-equatorial isomer dominates in all metal M-ed3a complexes [M = Co(III), Cr(III), Ni(II)] prepared so far [1,30]. 3.2.2. [Mg(H2O)5Cu(pd3a)][Cu(pd3a)] Æ 2H2O (2) The identification of the atoms and the configuration of the cation- and anion-moiety and the packing of the molecules are shown in Fig. 4. The asymmetric unit contains one formula unit, consisting of four moieties: a cationic

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Table 3 Configurational parameters correlating the square-pyramidal/trigonal-bipyramidal stereochemistry of ed3a-type of copper(II) complexes Configurational parameters ˚ ) in plane Cu–Nmean (A ˚ ) in plane Cu–Omean (A ˚ ) axial Cu–N (A ˚ ) axial Cu–O (A Tetragonality (T5) Trigonality s(%) ˚) q (A Reference a b c d

Pentadentate unit [Cu(ed3a)]a (1)

[Cu(ed3p)] (4)

[Cu(edtp)]b (5)

[Cu(pd3a)]c (2)

[Cu(pd3p)]d (3)

2.079 1.953 2.222 2.334 0.837 (T6) 17.5 0.0796 this work

1.988 1.970

2.026 1.956

2.010/1.991 1.926/1.911

2.115 2.046 2.317

2.181 0.903 42.2 0.222 [18]

2.173 0.900 29.2 0.195 [31]

2.138/2.233 0.900/0.856 11.50/12.17 0.142/0.216 this work

0.913 33.17 this work

˚ ). Assuming this octahedral molecule as square-pyramidal one without its longest axial Cu–O bond (2.334 A This unit contains penta-coordinated Cu(II) ion. Unit 1/Unit 2. Structural data taken from the most stable isomer calculated by the DFT theory.

Fig. 3. Overlay of (a) Ni(ed3a) and Cu(ed3a) complexes and (b) coordinated ed3a ligands.

[Mg(H2O)5Cu(pd3a)] complex (unit 1), anionic [Cu(pd3a)] complex (unit 2) and two solvent water molecules. Therefore, monoclinic unit cell (P21/c, Z = 4) contains 16 units, four cations, four anionic moieties and eight water molecules (Fig. 4a). A search of the distances yielded intermolecular- and intramolecular-contacts shorter than the sum of the van der Waals radii [32] for the atoms: the moieties are linked by hydrogen bonds [32–35] forming an infinite three-dimensional network along the base vectors (Fig. 4b). The square-pyramidal [Cu(pd3a)] complex has been found in two moieties as stated above. They actually differ ˚ unit 1 and 2.234 A ˚ only in axial Cu–O length: 2.137(5) A unit2. This is understandable if coordination of the carbonyl O14 toward the pentahydrated Mg cation is considered; this accounts for lowering of Cu(pd3a) negativity from unit 1 and therefore enables stronger Cu–O13 interaction. These two SPy Cu-pd3a units with Cu(II) caught in N2O3 cage are moderately distorted. The Jahn–Teller distortion [9] for Cu(II) gives rise to, this time expectedly, distorted SPy geometry for [Cu(pd3a)]. In the crystal structure (see Fig. 3a) the copper(II) ion coordinates five donor atoms from the pd3a ligand: deprotonated acetate oxygens and two amine nitrogen atoms (secondary and ter˚ tiary). The distances are within the range 1.915 and 2.137 A ˚ for unit 1 and 1.910–2.234 A for unit 2 (see Table 2). This is comparable with those obtained for related Cu(ed3p) and

Fig. 4. (a) ORTEP view of (2) with the scheme of atom numbering and (b) packing in the unit cell along c axis.

Cu(edtp) complexes [18,31]. The copper atoms show large displacement from the average plane defined by the donor ˚ unit 1; q = 0.216(1) A ˚ unit 2). The atoms (q = 0.142(1) A cis angles at the copper(II) ions range from 83.1(3) to 101.4(2) (unit 1) and 81.3(3) to 95.8(2) (unit 2) and the trans angles from 166.8(3) to 173.6(3) unit 1 and from 163.6(3) to 170.9(3) unit 2 showing moderate distorsion. Though at a first glance unit 1 and 2 look rather similar, detailed examination does reveal slight differences. For

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instance, both units contain two acetate rings in twistedenvelope conformation and one acetate ring almost planar. On the other side the different units rearrange these rings in a different way. Unit 1 contains quasi planar acetate in the axial position and similar acetate ring is found in the equatorial plane in unit 2. We shall keep our attention on axial acetate rings: five-membered acetate ring Cu21O21˚, C21C22N21 (with puckering parameters q2 = 0.336(7) A u2 = 344.3(16)) from unit 2 adopts twisted-envelope and Cu1O13C14C13N11 ring (with no puckering parameters because pseudorotation parameter s = 3.6 < 5) from unit 1 retrieved nearly planar frame. The six-membered backbone 1,3-propanediamine rings are nearly the same in both units: Cu1N11C15C16C17N12 ring (with pucker˚ , h = 24.3(8) and u = ing parameters Q = 0.552(10) A 174(2)) from unit 1 adopts favored chair conformation the one found in Cu2N21C25C26C27N22 ring of unit 2 ˚ , h = 0.690(8) (with puckering parameters Q = 0.690(8) A and u = 168.5(7)). 3.3. Geometry and configurational analysis of copper(II) ed3a-type complexes Structural data correlating the stereochemistry of copper(II) complexes containing ed3a-type and related ligands are given in Table 3. All considered complexes adopt SPy surrounding of the Cu(II) ion with ligating atoms (2N and 2O) being coordinated in the G-plane and carboxylato oxygen atom in the axial position. Exceptions are octahedral Cu(ed3a) complex where, for the correlation purpose, ˚ has been abstracted the longest Cu–O2 distance 2.334 A and square-pyramidal Cu(pd3p) complex for which the NO3 in plane and N(tertiary) axial chromophore has been calculated by DFT ADF2006.01 calculations (see Section 3.4). However, all the complexes are compared regarding to their N2O3 chromophore from the corresponding chelate. The extent of axial elongation in complexes is restricted by chelation of multidentate ligands forming five or sixmembered rings. The complexes 2–5 have distorted SPy geometry. The axial bonds of complexes 2,4 and 5 are ˚ ) but this not so different (range from 2.138 to 2.233 A range is extended in case of 1 and 5 (2.334 for complex 1 and 2.311 for complex 2). It seems that if the chelate rings are of the same size (five-membered in case of ed3a and sixmembered in case of pd3p) the extent of axial elongation is more pronounced. In structures 2–5 (Table 3) the four copper–ligand distances in the equatorial-plane are of normal ˚ ; average length (average Cu–N range from 1.988 to 2.115 A ˚ Cu–O range from 1.911 to 2.046 A). Exception can be found in Cu(pd3p) complex where slightly longer Cu–O and Cu–N distances are caused by optimizations of geometry in gaseous state or better to say solid state influence on the crystal structure. The tetragonality (T5) (given for oxygen ligands and nitrogen only in case of 3) ranges from 0.856 to 0.913. The bond length and the tetragonality data, obtained for the listed complexes, are as expected for

square-pyramidal complexes with mixed nitrogen–oxygen ligands [36–38]. The Cu(II) ions of these complexes are dis˚ ) from the equaplaced by distance q (q = 0.0796–0.222 A torial plane towards the apical ligand. The value s for the listed complexes varies from 11.5% to 42.2% indicating that these structures span the range of trigonally distorted square-pyramidal Cu(II) stereo-chemistries. However, as a rational observation (Table 3) we would state: the more six-membered rings the more pronounced trigonality. 3.4. Computational chemistry Computational chemistry allows the possibility of modeling metal complexes, providing structural and energetic information. ADF (Amsterdam density functional) is a Fortran program for calculations on atoms and molecules. It can be used for the study of Cu(II) complexes [27]. The underlying theory is the Kohn–Sham approach to the density functional theory (DFT). This implies a one-electron picture of the many-electron systems but yields in principle the exact electron density (and related properties) and the total energy. We have optimized geometries of each of the potential geometric isomers (Fig. 1). For the searching of global minima purpose we have chosen Becke exchange and Perdew correlation gradient corrections (also called BP) as this proved to be the best choice in our case. In each case we tried to optimize geometries of all the hypothetic geometrical isomers (cis-equatorial, cis-polar and trans see Fig. 1). First, we preoptimized particular isomer by molecular mechanics MM+ (Hyperchem7.01 [39]) and then left the structures to be optimized by ADF2006.01. In cases where we had crystal structures we used them directly for optimization. Since copper atom has one unpaired electron and doublet multiplicity the systems were treated within the unrestricted formalism. The complexes were left for full optimizations without restrictions (symmetry, restrains or constrains). Only in case of (1) we additionally run a geometry optimization under restrained Hw–Ow–Hw–Cu torsion angle. We wish here to point out that coordinated water in all six-coordinated complexes being optimized has been obstructive factor in obtaining correct final geometry. To be more precise, formation of the intra-molecular hydrogen bonds between water hydrogens and in-plane acetate oxygens obstructs obtaining of correct configuration of optimized molecules. To correct this anomaly we restricted HO(w)HCu torsion angle to value of 3350 the one close to the experimental one. This kind of calculation was much more time consuming but the optimized geometry has been more realistic. Our concern has been focused to obtain energies of the optimized structures and therefore to find out the most stable geometric isomer for each kind of complex species, Generally speaking, the theory follows the experiment. For all complexes where we have structural data the ADF theory gave the lowest energy for the isomer in question (Table 4). In case of Cu(pd3p) (3) complex we tried to model the most stable isomer starting from hexa- and

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Table 4 Difference in total bonding energya (calculated by ADF) (kcal/mol) correlating different isomers of ed3a-type-copper(II) complexes Geometrical isomer

[Cu(ed3a)]

[Cu(ed3p)]

CNb cis-Equatorial cis-Polar Trans

6 0 0.90 2.53

5 5.36 0 1.09

a b

[Cu(pd3a)] 6 0 1.69 2.44

5 7.19 0 2.58

[Cu(pd3p)] 6 10.32 0 2.85

5 3.03 0 2.38

6 0.89 0 1.73

The isomer with the lowest energy minimum has been indicated with 0 kcal/mol. CN = coordination number.

penta-coordinated complex (i.e. with or without coordinated water molecule). The same procedure has been applied in all cases except for Cu(ed3a) complex as it has been found in an octahedral environment. As might be seen from Table 4. DFT theory shows that cis-equatorial isomer is more stable for 0.90 kcal/mol than cis-polar and for 2.53 kcal/mol than trans one. This is not particularly great energy difference and may indicate, according to energetic similarity between cis-equatorial and cis-polar, existance of the latter in the reaction mixture. The most striking feature is the fact that the most stable isomer in all the other complexes, either penta- or hexacoordinated Cu(II), has been found as the cis-polar one. An exception apart from this rule is cis-equatorial isomer of hexacoordinated Cu(ed3p) being stable for 1.69 kcal/ mol more from cis-polar one. In fact this indicates that in case of the ed3a-type ligands other than ed3a ligand the favourable position of ligating atoms in Cu(II) complexes should be searched in a square-pyramidal surrounding. It is only cis-polar isomer of octahedral complexes for which there are no hard energetic nor configurational requirements to adopt SPy geometry by relieving a water molecule from an axial position (see Fig. 1). Table 5 contains structural parameters correlating ADF and experimental data (where we have it) of ed3a-type of copper(II) complexes. It is obvious from Table 5 that all the Cu–O and Cu–N bonds are sometimes significantly and sometimes slightly longer than ones found in crystal structures (ranging differ˚ ). This might be attributed to the ence from 0.058 to 0.267 A DFT calculations on molecules in gaseous state but also to the choice of exchange and correlation gradient potentials. As we stated above BP exchange-correlation gradient

potential gave, in our case, the best results when comparing with Becke (exchange) with the Lee–Yang–Parr 1988 correlation correction (so-called BLYP) or OPTX exchange correction proposed in 2001 by Handy–Cohen and PBEc the correlation term presented in 1996 by Perdew–Burke–Ernzerhof (so-called OPBE) xc-functionals. We think that using Slater-type orbital (STO) basis sets of triple-n quality with polarization functions (basis set IV or TZP) for all the calculations has an advantage over DZ or DZP (basis sets II and III) giving more realistic picture about complexes in question. When we correlate optimized geometries with corresponding X-ray structures in an overlay fashion the RMS error of medium quality have been obtained (Table 5). The overlayed structures of prepared complexes are shown in Fig. 5. 3.5. Spectral analysis The asymmetric carboxylate stretching frequencies have been established as criteria for distinguishing between protonated carboxylate groups (1700–1750 cm1) and coordinated carboxylate groups (1600–1650 cm1) [40–42]. The IR data reported here for diaminotricarboxylate copper(II) complexes support the above trend regarding the asymmetric frequencies of carboxylate groups. In addition, it has been demonstrated that the asymmetric stretching frequency of the carboxylate groups of the five-membered rings lies at higher energy than the corresponding frequency of the six-membered chelate rings [10]. The frequencies at 1603 and 1607 cm1 were assigned to the moieties of the five-membered acetato arms of Cu-ed3a and Cu-pd3a complexes, respectively; lower energy frequencies at 1583 cm1 was assigned to the moieties of the

Table 5 Structural parameters correlating experimental and ADF data of ed3a-type of copper(II) complexes Structural parameters ˚ ) in-planes Exp:DFT Cu–N (A

[Cu(ed3a)]

[Cu(ed3p)]

[Cu(pd3a)]

[Cu(pd3p)]

2.080:2.291 1.940:2.084 1.980:2.014

2.004:2.128 1.978:2.113 1.910:2.001 1.913:2.003

2.115

˚ ) in-plane Exp:DFT Cu–O (A

1.977:2.244 2.000:2.162 1.956:2.012 1.986:2.026

˚ ) axial Exp:DFT Cu–N (A ˚ ) axial Exp:DFT Cu–O (A ˚ )a RMS error (A

2.222:2.119 2.334:2.004 0.2289 with H2O; 0.25845

2.181:2.148 0.32911

2.233:2.380 0.3150

a

With respect to overlay of molecules obtained from X-ray data and from DFT calculations.

1.969 2.100 2.115 2.317

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Fig. 5. Overlay of ADF-calculated and X-ray structures of (a) Cu(ed3a)(H2O), (b) Cu(ed3p) and (c) Cu(pd3a).

six-membered 3-propionate arms of Cu-pd3p complex. The lack of other absorptions in the 1700–1750 cm1 range in the spectra of these complexes suggests that all the carboxylate groups are coordinated. The ligand field absorption spectra for (1), (2) and (3) complexes are given in Fig. 6. The holohedrized symmetry of octahedral complexes is D4h and that of square-pyramidal is C4v. All the complexes given in Fig. 6 exhibit a single quasi-symmetric [complexes (1) and (3)] or asymmetric [complex (2)] band. The Cu(ed3p) complex exhibits also one quasi-symmetric band at 14.66 kcm1 (e = 285.9) [31]. In general, these bands can be assigned to the dz2 , dxy, dxz, dyz ! dx2 y 2 transitions with a dx2 y 2 ground state that should be in agreement with their C4v (or D4h symmetry). The data measured for the reflectance spectra with respect to those taken from solution show that the complexes (2) and (3) have the same (a square-pyramidal) geometry in both states. The main difference between spectra, given in Fig. 6 including Cu(ed3p), reflects in their positions of the absorption maxima and band intensities. The energy of absorption maxima for SPy complexes increases in the order: Cu(pd3p) < Cu(ed3p)
Fig. 6. Absorption spectra of ed3a-type copper(II) complexes: Cu(ed3a)(H2O) (1); Cu(pd3a) (2); Cu(pd3p) (3).

respectively. This is further explanation for the lower energy of d–d transitions for Cu(ed3p) and (3) with respect to (1). The absorption intensity for (2) and (3) is lower than that found for the complex (1) (see Section 2). This lower intensity might be expected because of the less rigid sixmembered 1,3-propanediamine framework, as has been observed for the similar systems [1–4]. 4. Supplementary material CCDC 628340 and 628341 contain the supplementary crystallographic data for 1 and 2. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/ conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: [email protected]. Acknowledgment The authors are grateful to the Serbian Ministry for Science and Environment protection for financial support. (Project No. 142013B). References [1] D.J. Radanovic´, Coord. Chem. Rev. 54 (1984) 159, and references therein. [2] B.E. Douglas, D.J. Radanovic´, Coord. Chem. Rev. 128 (1993) 139. ˇ . Matovic´, Z.D. Matovic´, L.P. Battaglia, G. [3] D.J. Radanovic´, V.C Pelizzi, G. Ponticelli, Inorg. Chim. Acta 237 (1995) 151. [4] Z.D. Matovic´, G. Pelosi, S. Ianelli, G. Ponticelli, D.D. Radanovic´, D.J. Radanovic´, Inorg. Chim. Acta 268 (1998) 221. [5] J.L. Hoard, C.H.L. Kennard, G.S. Smith, Inorg. Chem. 2 (1963) 1316. [6] L.E. Gerdom, N.A. Beanziger, H.M. Goff, Inorg. Chem. 20 (1981) 1606. [7] J.D. Bell, G.L. Blackmer, Inorg. Chem. 12 (1973) 836. [8] G.H.Y. Lin, J.D. Leggett, R.M. Wing, Acta Crystallogr., Sect. B 29 (1973) 1023. [9] H.A. Jahn, E. Teller, Proc. R. Soc. London 161 (1937) 220. [10] Z.D. Matovic´, B. Ristic´, M. Joksovic´, S.R. Trifunovic´, G. Pelosi, S. Ianelli, G. Ponticelli, Transition Met. Chem. 25 (2000) 720. [11] Z.D. Matovic´, V.D. Miletic´, G. Samardzˇic´, G. Pelosi, S. Ianelli, S. Trifunovic´, Inorg. Chim. Acta 358 (2005) 3135. [12] E.J. Corey, J.C. Bailar Jr., J. Am. Chem. Soc. 81 (1959) 2620.

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