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Thiocyanato-metal(II) and azido-cobalt(III) complexes with hydroxymethylpyridines
Polyhedron 161 (2019) 309–316
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Thiocyanato-metal(II) and azido-cobalt(III) complexes with hydroxymethylpyridines Franz A. Mautner a,⇑, Magdalena Traber a, Patricia Jantscher a, Roland C. Fischer b, Klaus Reichmann c, Ramon Vicente d, Noor Arafat e, Salah S. Massoud e a
Institut für Physikalische and Theoretische Chemie, Technische Universität Graz, A-8010 Graz, Austria Institut für Anorganische Chemie, Technische Universität Graz, A-8010 Graz, Austria Institut für Chemische Technologie von Materialien, Technische Universität Graz, A-8010 Graz, Austria d Department de Química Inorgànica, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain e Department of Chemistry, University of Louisiana at Lafayette, Lafayette, LA 70504 USA b c
a r t i c l e
i n f o
Article history: Received 25 November 2018 Accepted 12 January 2019 Available online 24 January 2019 Keywords: Isothiocyanate Copper Nickel Zinc Crystal structure
a b s t r a c t A dimeric [Cu(l-4-HOMP)(4-HOMP)(NCS)2]2 (1) and three discrete monomeric complexes [Ni(3-HOMP)2 (NCS)2(H2O)2] (2), [Co(3-HOMP)3(N3)3]H2O (3) and [Zn(4-HOMP)2(NCS)2] (4), (3-HOMP = 3hydroxymethylpyridine, 4-HOMP = 4-hydroxymethylpyridine) have been isolated and structurally characterized by IR, UV–Vis spectroscopy, XRPD, single crystal X-ray crystallography and Hirshfeld surface analysis as well as thermogravimetric analyses for complexes 1, 2 and 4. In dimeric complex 1 each penta-coordinated Cu2+ center is bridged through N,O-4-HOMP ligands, whereas metal ions in 2 and 3 are located in distorted octahedral geometry with mer-configuration in the azido complex 3. Distorted tetrahedral geometry is observed around Zn2+ in complex 4. The variable temperature magnetic susceptibility measurements of 1 showed very weak antiferromagnetic interaction. Ó 2019 Elsevier Ltd. All rights reserved.
1. Introduction Thiocyanato, NCS and azido, N 3 pseudo halides have been extensively used as bridging ligands in the construction of coordination polymers (CPs) and high nuclearity clusters with 3d metal ions and building block organic molecules [1–9]. The diversity of bonding modes of NCS and N 3 in metal complexes, which were summarized in some recent reports [1,7], led to the creation of compounds of potential applications in the field of luminescence [8] and molecular magnetism [1–7]. In bridging thiocyanato and azido compounds, the ions have the potential to mediate ferroand antiferro-magnetic coupling between the bridged paramagnetic metal ions resulting in interesting magnetic phenomena such as single molecule magnets (SMMs) and single chain magnets (SCMs) [1–7]. In discrete mononuclear thiocyanato- and azido-metal complexes, where NCS and N 3 are acting as terminal ligands only one coordination bonding site exists in the latter case, whereas in the NCS compounds two possible modes may be found due to the ambidentate nature of the ligand. Soft metal ions prefer
⇑ Corresponding author. E-mail address: [email protected] (F.A. Mautner). https://doi.org/10.1016/j.poly.2019.01.030 0277-5387/Ó 2019 Elsevier Ltd. All rights reserved.
binding through the S-site and hard metals prefer the N-site [10]. Although the nitrogen in NCS is categorized as at the borderline Lewis bases according to HSBA concept [10], most hard metals showed high preference to the N-site [11]. The metal ion’s preference to any of the coordination bonding sites in NCS complexes may change depending on a number of factors which include electronic nature and oxidation state of metal ion, the nature of the coordinated ancillary co-ligand(s) and the steric hindrance imposed by the coligand(s) surrounding the central metal ion [12]. The number of pseudohalide metal complexes with 3-hydroxymethylpyridine (3-HOMP) and 4-hydroxymethylpyridine (4HOMP) is quite limited due to lack of N,O-chelating modes in these species. In contrast, different azide bridging modes were observed in the polymeric chains of [M(L)y(N3)2]n (M = Cd [13] and Cu [7c], L = 3- or 4-hydroxymethylpyridine). Similarly bis-l1,5-dicyanamide (dca) bridges have been found in case of [M(4-HOMP)2(dca)2]n 1D systems (M = Co, Cu) [14]. Moreover, Näther et al. reported several series of mononuclear and polymeric isocyanate complexes with 4-HOMP co-ligand with Co [15], Ni [16] and a 3D network structure with Cd [17], in addition to a series of six Cd- and Zn-isocyanate complexes with 3-HOMP co-ligand [18]. Interestingly, the iron complex [Fe(3-HOMP)2(NCS)4] with the 3-HOMP co-ligands are N-coordinated to the Fe(III) ion, crystallizes
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with the protonation of 3-HOMP; HOMPH+ counter cations and neutral 3-HOMP solvent molecules [19]. In this paper, we explore the coordination chemistry of thiocyanato complexes with the borderline Lewis acids Cu2+, Ni2+ and Zn2+and azido-Co3+ complex with 3- and 4-hydroxymethyl- pyridine compounds namely: the dimeric [Cu(l-4-HOMP)(4-HOMP) (NCS)2]2 (1) and the monomeric species [Ni(3-HOMP)2(NCS)2(H2OH2O)2] (2), [Co(3-HOMP)3(N3)3]H2O (3) and [Zn(4-HOMP)2(NCS)2] (4).
2. Experimental
2.2.3. [Co(3-hydroxymethylpyridine)3(N3)3]H2O (3) A mixture of Co(NO3)26H2O (0.290, 1 mmol), NaN3 (0.13 g, 2 mmol) and 3-hydroxymethylpyridine (0.22 g, 2 mmol) are dissolved in 20 mL distilled H2O. The solution is stirred for 30 minutes at 75–80 °C, filtered while hot and then allowed to stand at room temperature (24–25 °C). The thin dark green well shaped needles, which were separated after 2 weeks, were collected by filtration (yield: 0.32 g, 90%). Anal. Calc. for C18H23CoN12O4 (530.41 g/mol): C, 40.8; H, 4.4; N, 31.7%. Found: C, 40.6; H, 4.3; N, 31.9%; (ATRIR, cm1): 3303 (s,br), 2008 (vs), 1606 (m), 1583 (w), 1478 (m), 1458 (w), 1431 (m), 1356 (mw), 1283 (s), 1203 (m), 1185 (m), 1110 (m), 1023 (s), 966 (m), 923 (m), 841 (w), 828 (w), 801 (m), 699 (w), 669 (m), 585 (m), 449 (w), 430 (w).
2.1. Materials and physical measurements 3-Hydroxymethylpyridine and 4-hydroxymethylpyridine were purchased from TCI and the other chemicals were of analytical grade quality. Infrared spectra of solid complexes were recorded on a Bruker Alpha P (platinum-ATR-cap) spectrometer. UV–Vis spectra were performed with a LS 950 Perkin-Elmer Lambda-spectrometer. Elemental microanalyses were carried out with an Elementar Vario EN3 analyser. Bulk phase purity of the title compounds was examined with a Bruker D8 Advance X-ray powder diffractometer (Figs S1–S4 in the supplementary materials section). A NETSCH STA 409 was used for thermoanalysis (heating rate: 10 °C/min, inert gas flow: 40 ml N2/min). Magnetic susceptibility measurements for 1 under 1 T magnetic field in the range 2–300 K and magnetization measurements in the field range of 1–4 T were performed with a Quantum Design MPMS-XL SQUID magnetometer at the Magnetochemistry Service of the University of Barcelona. All measurements were performed on polycrystalline samples. Pascal’s constants were used to estimate the diamagnetic corrections, which were subtracted from the experimental susceptibilities to give the corrected molar magnetic susceptibilities. Caution: Azido complexes and their salts are potentially explosive. Only small quantities should be handled with great care.
2.2. Synthesis of the complexes 2.2.1. [Cu(4-hydroxymethylpyridine)2(NCS)2]2 (1) A mixture of Cu(NO3)23H2O (0.48 g, 2 mmol), KSCN (0.39 g, 4 mmol) and 4-hydroxymethylpyridine (0.44 g, 4 mmol) were dissolved in 35 mL distilled H2O. The solution was heated up to 70 °C and stirred for 2 h. After filtration the green solution was stirred again for 20 min at the same temperature and then cooled down to RT. After a few hours small green crystals were obtained (yield: 0.54 g, 68%). Anal. Calc. for C14H14N4O2S2Cu (397.97 g/mol): C, 42.25; H, 3.55; N, 14.08; S, 16.11; Found: C, 42.19; H, 3.58; N, 14.15; S, 15.60%. IR (ATR, cm1): 3456 (w), 3275 (m), 2093 (vs), 1616 (m), 1561 (w), 1504 (w), 1423 (s), 1365 (m), 1195 (w), 1101 (vw), 1050 (m), 1019 (s), 801 (vs), 743 (w), 714 (w), 665 (w), 610 (m), 513 (w), 490 (m), 462 (m).
2.2.4. [Zn(4-hydroxymethylpyridine)2(SCN)2] (4) A mixture of ZnCl2 (0.13 g, 1 mmol), KSCN (0.19 g, 2 mmol) and g 4-hydroxymethylpyridine (0.22 g, 2 mmol) was dissolved in 15 mL distilled H2O. The solution was heated up to 55–60 °C and stirred for 1 h. After filtration, the clear solution was stirred again for 1 hour (50 °C) and then cooled down to room temperature. After 24 h clear colorless crystals were obtained (yield: 0.33 g, 83%). Anal. Calc. for C14H14N4O2S2Zn (399.81 g/mol): C, 42.06; H, 3.53; N, 14.01; S, 16.04%. Found: C, 41.84; H, 3.54; N, 14.00; S, 15.89%. IR (ATR, cm1): 3409 (s,br), 2075 (vs), 1621 (s), 1562 (w), 1508 (vw), 1452 (w), 1429 (m), 1340 (w), 1277 (w), 1224 (m), 1105 (w), 1034 (s), 949 (w), 807 (m), 722 (w), 657 (vw), 607 (m), 472 (s). 2.3. X-ray crystal structure analysis The X-ray single-crystal data of the four compounds were collected on a Bruker-AXS APEX CCD diffractometer at 100(2) K. The crystallographic data, conditions retained for the intensity data collection and some features of the structure refinements are listed in Table 1. The intensities were collected with Mo Ka radiation (k = 0.71073 Å). Data processing, Lorentz-polarization and absorption corrections were performed using APEX, and the SADABS computer programs [20]. The structures were solved by direct methods and refined by full-matrix least-squares methods on F2, using the SHELX program package [21]. All non-hydrogen atoms were refined anisotropically. The hydrogen atoms were located from difference Fourier maps, assigned with isotropic displacement factors and included in the final refinement cycles by use of geometrical constraints. In case of 1, a two-fold disorder with occupancy of 0.50 was observed for pyridine carbon atoms C (10)–C(13) and C(20)–C(23), respectively. Also in 3 for atoms of two-fold disordered hydroxymethyl groups split occupancies of 0.492(5)/0.508(2) for O(1)–C(6), 0.826(5)/0.174(5) for O(2)–C(12), 0.638(4)/0.362(4) for O(3)–C(18), respectively, were applied. The Molecular plots were performed with the Mercury program [22]. 3. Results and discussion 3.1. Synthesis of the complexes
2.2.2. [Ni(3-hydroxymethylpyridine)2(NCS)2(H2O)2] (2) Complex 2 was synthesized in a similar procedure as that described for 1 but with using NiSO46H2O (0.52 g, 2 mmol) and 3-hydroxymethylpyridine (0.44 g 4 mmol) instead. After 6 days at room temperature (approx. 25 °C) blue to turquoise regularshaped crystals were separated. These were collected by filtration (yield: 0.53 g, 62%). Anal. Calc. for C14H18N4NiO4S2 (429.15 g/mol): C, 39.2; H, 4.2; N, 13.1%. Found: C, 40.0; H, 4.0; N 13.4%; (ATR-IR, cm1): 3008 (w,br), mCN: 2098 (vs), 1733 (w), 1635 (w), 1481 (m), 1460 (s), 1432 (w), 1324 (w), 1188 (s), 1131 (m), 1059 (m), 936 (w), 807 (m), 756 (w), 706 (w), 649 (w), 608 (s), 458 (s).
Reactions of aqueous solutions containing the stoichiometric 1:2:2 molar ratios of Cu(NO3)23H2O, NiSO46H2O or ZnCl2, KNCS and 3- or 4-hydroxymethylpyridine afforded the dimeric [Cu(l4-HOMP)(4-HOMP)(NCS)2]2 (1) as well as the discrete monomeric complexes [Ni(3-HOMP)2(NCS)2(H2O)2] (2) and [Zn(4-HOMP)2 (NCS)2] (4) in moderate to high yields with good quality single crystals. Analogous reaction of an aqueous solution of Co(NO3)26H2O with two equivalents of 3-hydroxymethylpyridine and in the presence two equivalents of NaN3 yielded dark green needles of [Co(3-HOMP)3(N3)3]H2O (3), where Co2+ was slowly oxidized by
F.A. Mautner et al. / Polyhedron 161 (2019) 309–316 Table 1 Crystallographic data and processing parameters for 1–4. Compound
1
2
Empirical formula Formula mass System Space group
C28H28Cu2N8O4S4 795.92 monoclinic P21/c
C14H18N4NiO4S2 429.15 triclinic
a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z T (K) l (mm1) Dcalc (Mg/m3) Crystal size (mm) h max (°) Data collected Unique reflections (Rint) Parameters Goodness-of-Fit (GOF) on F2 R1/wR2 (all data) Residual extrema (e/Å3)
10.9582(14) 19.6859(18) 8.0786(12) 90 111.469(2) 90 1621.8(4) 2 100(2) 1.617 1.630 0.26 0.20 0.13 25.284 11 792 2935/0.0626 250 1.374 0.0880/0.1735 0.99 and 0.73
Compound Empirical formula Formula mass System Space group
3 C18H23CoN12O4 530.41 Triclinic
a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z T (K) l (mm1) Dcalc (Mg/m3) Crystal size (mm) h max (°) Data collected Unique reflections (Rint) Parameters Goodness-of-Fit (GOF) on F2 R1/wR2 (all data) Residual extrema (e/Å3)
P1 9.5389(7) 10.1934(8) 12.2606(9) 96.070(3) 108.146(3) 93.517(4) 1120.88(15) 2 100(2) 0.820 1.572 0.23 0.16 0.11 30.089 68 273 6570/0.0283 367 1.063 0.0337/0.0904 1.16 and 0.52
P1 7.6565(8) 8.6363(11) 8.7184(11) 67.363(2) 65.653(2) 66.934(2) 465.76(10) 1 100(2) 1.291 1.530 0.38 0.28 0.15 26.324 3743 1866/0.0223 124 1.092 0.0235/0.0612 0.25 and 0.28 4 C14H14N4O2S2Zn 399.18 Monoclinic P2/n 18.3490(15) 5.0296(3) 18.8817(17) 90 95.910(4) 90 1733.3(2) 4 100(2) 1.670 1.532 0.27 0.19 0.11 26.328 12 908 3529/0.0350 215 1.114 0.0429/0.0979 0.83 and 0.29
air upon standing at room temperature. The purity of the synthesized complexes was examined by elemental microanalyses and their bulk phase purity by XRPD. The complexes were also investigated by IR and UV–Vis spectroscopy, and Hirshfeld surface calculations as well as thermogravimetric analysis for 1, 2 and 4. 3.2. IR and UV–Vis spectra of the complexes The IR spectra of the complexes under investigation display some general characteristic features. In addition of the vibrations of the methylpyridine moiety, very strong absorption bands observed at 2093 cm1 (1), 2098 cm1 (2), and 2075 cm1 (4) are due to the asymmetric stretching frequencies of the coordinated NCS ligands. The appearance of mas(NCS) at a frequency value <3100 cm1 is more consistent with N-NCS bonding [11], whereas complex 3 shows the very strong mas(N3) vibration of the azide groups at 2008 cm1 [7]. The four title complexes display medium to strong broad bands above 3000 cm1, respectively due to m(OH) of the aqua ligand, water of crystallization and/or the hydroxyl O– H stretching vibration of hydroxymethylpyridine molecules [14]. The UV–Vis spectrum of solid copper(II) complex 1 displays a broad absorption band centered around 612 nm accompanied with
311
a low-energy shoulder at k > 800 nm. This feature is consistent with five-coordinate Cu(II) complexes with square pyramidal geometry (SP) [7,8c]. The UV–Vis spectrum of solid nickel(II) complex 2 displays three maxima at 372, 606 and 973 nm. These spec3 tral bands are assigned to the electronic transitions 3T1g(P) A2g, 3 3 3 T1g(F) A2g and 3T2g A2g, respectively for Ni(II) in octahedral environment [23–25]. The UV–Vis spectrum of solid cobalt(III) complex 3 shows a broad absorption band centered at 610 nm which corresponds to the electronic transition 5E T2 of octahedral Co(III) in weak ligand field environment [23–25]. 3.3. Description of the crystal structures 3.3.1. [Cu(l-4-HOMP)(4-HOMP)(NCS)2]2 (1) A perspective view of 1 is given in Fig. 1, a packing view is in Fig. S5 in the supplementary materials section, and selected bond parameters are summarized in Table 2. The Cu(1) metal center is penta-coordinated by N(1) and N(2) atoms of two terminal isothiocyanato anions, by N(3) of a terminal 4-hydroxymethylpyridine molecule, further by O(2) and N(40 ) atoms of two l(N,O)-bridging 4-hydroxymethylpyridine molecules, which connect Cu(1) and Cu(10 ) polyhedra to form centrosymmetric dinuclear units. The CuN4O chromophore may be described as slightly distorted square pyramid (SP) with a s-value of 0.03 [s-values of 1 and 0 refer to ideal geometries of trigonal bipyramid (TBP) and square pyramid (SP), respectively] [26]. The apical site is occupied by O(2) [Cu (1)-O(2) = 2.379(5) Å]. The basal Cu–N bond distances are in the range from 1.954(6) to 2.041(6) Å. The terminal isothiocyanate anions have following bond parameters: N–C: 1.138(8) and 1.156 (9) Å, C–S: 1.644(7) and 1.637(8) Å, Cu–N–C: 170.8(6) and 169.0 (6)°, N–C–S: 178.0(7) and 178.7(7)°. The Cu(1) Cu(10 ) distance is 7.9083(18) Å and the shortest inter-dinuclear metal–metal separation is 5.8666(16) Å. Along the c-axis the Cu(1) S(200 ) [(00 ): x, y,1 z] separation is 3.117(2) Å. Hydrogen bonds of type O–H S between hydroxy-groups of pyridine derivative ligands and adjacent non-coordinated S atoms of terminal isothiocyanate anions form a supramolecular 2D system oriented along the b- and c-axis of the monoclinic unit cell [O(1)–H(91) S(2#1) = 155(3)°, O(1) S (2#1) = 3.454(7) Å; O(2)–H(92) S(1#2) = 172(4)°, O(2) S(1#2) = 3.168(5) Å; (#1): x,1/2 y,1/2 + z; (#2): x,1/2 y,1/2 + z]. In the crystal structures of [M(4-HOMP)2(NCS)2]n (M = Co [15], Ni [16]) the octahedrally coordinated metal(II) centers are linked into dimers by pairs of l(N,S)-bridging NCS anions and are further connected into chains by the l(N,O)-bridging 4-hydroxymethylpyridine molecules. 3.3.2. [Ni(3-HOMP)2(NCS)2(H2O)2] (2) A perspective view of 2, together with the atom numbering scheme is given in Fig. 2. The crystal structure of 2 consists of neutral mononuclear Ni(II) complexes. The Ni(1) atom is located at the
Fig. 1. Perspective view of 1. Symmetry code: (0 ) 1 x,y,1 z.
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Table 2 Selected bond lengths (Å) and angles (°) for compound 1–4. Compound 1 Cu(1)–N(1) Cu(1)–N(2) Cu(1)–N(3) N(1)–C(1) N(2)–C(2) N(2)–Cu(1)–N(1) N(1)–Cu(1)–N(3) N(1)–Cu(1)–N(40 ) N(2)–Cu(1)–O(2) N(3)–Cu(1)–O(2) Cu(1)–N(1)–C(1) Cu(1)–N(2)–C(2)
1.973(6) 1.954(6) 2.028(6) 1.138(8) 1.156(9) 177.6(3) 88.9(2) 90.5(2) 93.0(2) 92.3(2) 170.8(6) 169.0(6)
Compound 2 Ni(1)–N(1) Ni(1)–O(2) C(7)–S(1) N(1)–Ni(1)–N(10 ) N(1)–Ni(1)–O(2) Ni(1)–N(3)–C(7)
2.1177(12) 2.0724(11) 1.6439(15) 180 91.15(4) 160.92(12)
Compound 3 Co(1)–N(1) Co(1)–N(7) Co(1)–N(11) N(1)–N(2) N(4)–N(5) N(7)–N(8) N(1)–Co(1)–N(11) N(4)–Co(1)–N(7) Co(1)–N(4)–N(5) N(1)–N(2)–N(3) N(7)–N(8)–N(9) Compound 4 Zn(1)–N(10 ) Zn(1)–N(3) N(1)–C(1) N(2)–C(2) N(1)–Zn(1)–N(10 ) N(10 )–Zn(1)–N(3) N(10 )–Zn(1)–N(30 ) N(3)–Zn(1)–N(30 ) Zn(1)–N(1)–C(1) Zn(2)–N(2)–C(2)
Cu(1)–N(40 ) Cu(1)–O(2) S(1)–C(1) S(2)–C(2)
2.041(6) 2.379(5) 1.644(7) 1.637(8)
N(2)–Cu(1)–N(3) N(2)–Cu(1)–N(40 ) N(3)–Cu(1)–N(40 ) N(1)–Cu(1)–O(2) N(4)–Cu(1)–O(20 ) N(1)–C(1)–S(1) N(2)–C(2)–S(2)
88.8(2) 91.8(3) 179.4(3) 87.8(2) 87.7(2) 178.0(7) 178.7(7)
Ni(1)–N(3) N(3)–C(7)
2.0454(13) 1.156(2)
N(3)–Ni(1)–O(20 ) N(30 )–Ni(1)–N(1) N(3)–C(7)–S(1)
91.07(5) 90.40(5) 178.99(13)
1.9448(13) 1.9571(13) 1.9936(13) 1.200(2) 1.1988(18) 1.200(2) 175.53(5) 176.58(5) 123.63(10) 176.11(18) 175.95(17)
Co(1)–N(4) Co(1)–N(10) Co(1)–N(12) N(2)–N(3) N(5)–N(6) N(8)–N(9) N(10)–Co(1)–N(12) Co(1)–N(1)–N(2) Co(1)–N(7)–N(8) N(4)–N(5)–N(6)
1.9628(12) 1.9695(12) 1.9607(12) 1.155(2) 1.1561(19) 1.151(2) 178.75(5) 121.14(11) 121.20(11) 176.14(16)
1.942(2) 2.018(2) 1.158(4) 1.159(4) 121.03(15) 103.53(9) 108.81(9) 111.16(13) 174.3(2) 169.0(2)
Zn(2)–N(200 ) Zn(2)–N(4) S(1)–C(1) S(2)–C(2) N(2)–Zn(2)–N(200 ) N(200 )–Zn(2)–N(4) N(200 )–Zn(2)–N(400 ) N(4)–Zn(2)–N(400 ) N(1)–C(1)–S(1) N(2)–C(2)–S(2)
1.939(2) 2.019(2) 1.627(3) 1.627(3) 124.27(15) 105.24(9) 105.90(10) 109.91(13) 177.6(3) 177.7(3)
minal N-coordinated NCS- anions are: Ni(1)–N(3)–C(7) = 160.93 (12), N(3)–C(7)–S(1) = 178.98(13)°, N(3)–C(7) = 1.156(2), C(7)–S (1) = 1.6439(15) Å. Further selected bond lengths and angles are listed in Table 2. The shortest metal–metal separation is 7.6565 (10) Å. A supramolecular three-dimensional network is formed by hydrogen bonds of type O–H S and O–H O (Fig. S6). [O(2)– H(91) S(1#1) = 158°, O(2) S(1#1) = 3.2535(16) Å; O(1)–H(92) S(1#2) = 146°, O(1) S(1#2) = 3.3309(14) Å; O(2)–H(90) O(1#3) = 177°, O(2) O(1#3) = 2.7320(19) Å; (#1): x,1 + y,z; (#2): 1 + x, y,1 + z; (#3): 2 x,y,2 z]. Analogous [Ni(py-R)2(NCS)2(H2O)] complexes with the following py-R (pyridine derivative ligand) have been structurally characterized: nicotinamide [27], 2,5-bis (4-pyridinyl)-1,3,4-thiadiazole [28], 5-nitroquinoline [29], pyridine-4-carboxylic acid [30,31], 1-(pyridin-4-yl)ethanone [32], 2chloropyridine [33], 3-methylpyridine [34], 4-hydroxymethylpyridine [16], 4-aminopyridine [35]. 3.3.3. [Co(3-HOMP)3(N3)3]H2O (3) A perspective view of 3, together with the atom numbering scheme is given in Fig. 3, a packing view in Fig. S7 and selected bond lengths and bond angles are given in Table 2. The crystal structure of 3 consists of neutral mononuclear [Co(3-HOMP)3(N3)3] complexes and lattice water molecules. The Co(1) center is octahedrally coordinated by six N-donor atoms (three of them from Npyridyl 3-HOMP molecules, and remaining three from terminal azido anions) in a mer-conformation. The Co(1)–N bond distances are in the range from 1.9448(13) to 1.9936(13) Å. The transoid N–Co(1)–N bond angles vary from 175.53(5)° to 178.75(5)° and the cisoid N–Co(1)–N bond angles are in the range from 87.29 (5)° to 93.66(5)°. The bond parameters of the terminal azido groups
Symmetry codes: for 1: (0 ) 1 x,y,1 z; for 2: (0 ) 2 x,1 y,1 z; for 4: (0 ): 3/2 x,y,1/2 z; (00 ): 3/2 x,y,3/2 z.
inversion center. It is six-coordinated by N(1), N(10 ) of two 3-hydroxymethylpyridine molecules, N(3) and N(30 ) of two isothiocyanato anions and O(2) and O(20 ) of two aqua ligands. The NiN4O2 chromophore may be described as distorted octahedron with Ni (1)–O/N bond distances in the range from 2.0454(13) to 2.1177(12) Å. The cisoid N–Ni(1)–O and N–Ni(1)–N bond angles are in the range from 88.85(4) to 91.15(4)°. The bond parameters of the ter-
Fig. 2. Perspective view of 2. Symmetry code: (0 ) 2 x, 1 y, 1 z.
Fig. 3. Perspective view of 3.
Fig. 4. The two crystallographic independent Zn(II) polyhedra of 4. Symmetry codes: (0 ): 3/2 x,y,1/2 z; (00 ): 3/2 x,y,3/2 z.
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313
Fig. 5. TG curves of 1 (top), 2 (middle) and 4 (bottom).
are: Co(1)–N–N: from 121.20(11) to 123.63(10)°; N–N–N: from 175.95(17) to 176.14(16)°; N(a)–N(b): from 1.1988(18) to 1.200 (2) Å; N(b)–N(c): from 1.151(2) to 1.1561(19) Å [with N(a) ligated to Co(1)]. The shortest metal–metal separation is 6.4581(6) Å. Oxy-
gen donor atoms of the two-fold disordered hydroxymethyl groups and of ordered non-coordinated water molecules form hydrogen bonds of type O–H O and O–H N: [O(3a)–H(3a) O(4#1) = 161°, O(3a) O(4#1) = 2.806(4) Å; O(4)–H(41) N(6#2) = 175°, O
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3.4. Thermoanaytical behavior
Fig. 6. vMT plot vs. T for compound 1.
(4) N(6#2) = 2.891(3) Å; O(4)–H(42) O(2a) = 113°, O(4) O(2a) = 2.703(3) Å; (#1): x,1 + y,z; (#2): x,y,1 z]. As far as we know, only six monomeric Co(III) complexes of composition [Co(pyR)3(N3)3] have been reported with following py-R: tris(2-pyridyl) methylamine [36], mer-configuration for py [37], 3,4- and 3,5dimethylpyridine [38], 4-methylpyridine [39], whereas fac-configuration was observed only once for a complex containing py and 2,20 -bipy simultaneously [40].
3.3.4. [Zn(4-hydroxymethylpyridine)2(NCS)2] (4) The crystal structure of 4 (perspective view is shown in Fig. 4, a packing view in Fig. S4 and selected bond parameters are listed in Table 2) consists of two crystallographically independent mononuclear neutral Zn(II) complexes. Each Zn(II) is tetrahedrally coordinated by N atoms of two terminal isothiocyanato anions, and by N atoms of two neutral 4-hydroxymethylpyridine molecules. The Zn–N bond distances are in the range from 1.942(2) to 2.018(2) Å, and the bond angles within the ZnN4 tetrahedron vary from 103.53(9)° to 124.3(2)°. The bond parameters of terminal N-coordianted NCS anions are: Zn–N–C = 169.0(2) and 174.3(2)°, N–C– S = 177.7(3)°, N–C = 1.159(4) and 1.158(4) A, C–S = 1.627(3) Å. The shortest metal–metal separation is 5.0296(8) Å. Hydrogen bonds of type O–H S form a supramolecular 2D system [O(1)–H (1) S(2#1)(#1: 3/2 x,1 + y,3/2 z) = 162(4)°, O(1) S(2#1) = 3.265(3) Å; O(2)–H(2) S(1#2)(#2: x,2 + y,z) = 171(4)°, O(1) S (2#1) = 3.239(3) Å]. A CSD search (version 5.39, updates Aug 2018) for monomeric [Zn(py-R)2(NCS)2] with tetrahedrally coordinated Zn(II) centers revealed 40 hits. Compilation of the bond parameters for 38 of the reported ZnN4 coordination figures gave the following results: Zn–N(NCS): from 1.911 to 1.963 Å, mean 1.934 Å, Zn–N(py) from 1.991 to 2.059 Å, mean 2.029 Å; N(NCS)– Zn–N(NCS): from 105.95° to 125.67°, mean 117.86°, N(py)–Zn–N(py): from 102.38 to 117.17°, mean 109.92°. Thus the Zn–N(py) bonds are by 0.078 Å longer, and the N(py)–Zn–N(py) angles by 12.11° smaller than the corresponding bond parameters of the N-terminal isothiocyanate anions. In case of the complex with 3-hydroxymethylpyridine (refcode: ZEMNAJ [18]) ‘‘inverted” bond parameters are observed: 1.988 vs. 1.966 Å and 109.41 vs. 109.95°. The sterical hindrance of the chelating bis-pyridyl ligands 1,10phenanthroline-N,N0 (refcode: TOBGIB [41]) and 6-bromo-N(pyridin-2-yl)pyridin-2-amine (refcode: FUZXIJ [42]) leads to much smaller N(py)-Zn-N(py) chelating angles of 81.62° and 94.66°, respectively. Interestingly, only the complex with isoquinoline ligands (refcode EFOXOO [43]) forms two crystallographically independent ZnN4 polyhedra and crystallizes as 4 in the space group P2/n.
The thermogravimetric heating curves of compounds 1, 2 and 4 are given in Fig. 5. Compounds 1 and 4 show the following four steps of weight loss (Dm): (1): 32.85% (from 102 to 238 °C), 25.56% (from 238 to 297 °C), 9.96% (from 297 to 438 °C), and 4.49% (from 438 to 980 °C); and (4): 24.10% (from 135 to 270 °C), 27.32% (from 270 to 359 °C), 6.84% (from 359 to 467 °C), and 8.49% (from 467 to 980 °C). The first two steps of weight loss in 1 and 4 may be attributed to the release of the hydroxymethylpyridine molecules, Compound 2 shows the following three steps of weight loss (Dm): 7.26% (from 85 to 170 °C), 57.68% (from 170 to 434 °C) and 7.94% (from 434 to 980 °C). In this case, the first two steps may be attributed to the loss of the two aqua ligands (Calcd: weight loss: 8.40%) followed by the release of the two 3-HOMP ligands (Calcd: weight loss: 50.86%). 3.5. Magnetic properties of [Cu(l-4-HOMP)(4-HOMP)(NCS)2]2 (1) The plot of vMT vs. T for compound 1 is shown in Fig. 6. Compound 1 shows a vMT value of 0.87 cm3 mol1 K at room temperature. This value is slightly higher than that expected for two uncoupled S = 1/2 spins (0.75 cm3 mol1 K, g = 2.0). Upon cooling the vMT values are practically constant, decreasing only from T < 25 K to a value of 0.78 cm3 mol1 K at 2 K. The vM values increase on cooling from 2.9 103 cm3 mol1 at 300 K without a maximum. This behavior indicates slight antiferromagnetic coupling or un-coupled dinuclear system. Based on the situation, the experimental magnetic data for 1 have been fitted using the Bleaˆ = JSˆA.SˆB with ney-Bowers expression based on the Hamiltonian H SA = SB = 1/2 (Eq. (1)).
vM ¼ 2Ng2 l2B =kT ½3 þ expðJ=kT Þ1
ð1Þ
Least-squares fitting on all experimental data led to the following parameters: J = 0.32(2) cm1, g = 2.13(1). 3.6. Hirshfeld surface analyses With the Hirshfeld surface calculations [44,45] it is possible to obtain three-dimensional pictures of close contacts in a crystal. The Hirshfeld surfaces of complexes 1–4 are presented in Figs. S9–S11, giving surfaces that have been mapped over dnorm, shape index and curvedness. A very useful supplement of the Hirshfeld surface calculations are the 2D fingerprint plots [45–47], giving a quantitative analysis of the nature and type of intermolecular interactions between complex molecules. With the 2D fingerprint plots it is possible to separate various intermolecular interactions to particular atom pair close contacts. E.g. the H O/O H interactions are represented by a spike in the 2D fingerprint plots [H O acceptor interactions as a spike in the bottom right region, O H donor interactions as a spike in the bottom left region], whereas in a full 2D fingerprint plot all possible contributions from different interactions are overlapped. The main contributions in the fingerprint plots are given in Figs. 7 and 8. For 1 (Fig. 7, top row): H C/C H 15.2%; H H 34.1%; H O/O H 6.0%; H S/S H 32.3% and C C 3.1%, remaining 9.1%. For 2 (Fig. 7, second row): H C/C H 17.0%; H H 30.2%; H O/O H 12.5%; H S/S H 27.4% and C C 5.3%, remaining 7.6%. For 4 (Fig. 7, third row): H C/C H 17.2%; H H 28.9%; H O/O H 5.9%; H S/S H 29.0% and C N/N C 8.7%, remaining 10.3%. For the azido complex 3 (Fig. 8: H C/C H 7.4%; H H 36.7%; H O/O H 14.9%; H N/N H 30.9% and C N/N C 5.4%, remaining 4.7%. For the isothiocyanato complexes the H S/S H contributions are in the range from 27.4 to 32.3%, whereas the
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Fig. 7. 2D fingerprint plots for 1 (first row), 2 (second row), and 4 (third row).
Fig. 8. 2D fingerprint plots for 3.
H O/O O are much lower from 5.9 to 12.5%, reflecting the dominance of the O–H S hydrogen bonds. In the azido complex 3 the O–H N hydrogen bonds dominate as the H N/N H contacts are approx. twice as large as the O H/H O contacts.
4. Conclusions To conclude, the interaction of the borderline Lewis acids Cu2+, Ni2+ and Zn2+ with ambidentate Lewis bases with hard/soft donor sites such as NCS- in the presence of 3- and 4-hydroxymethyl- pyridine as coligands to form mono- or di-nuclear metal complexes results in the formation of species [Cu(l-4-HOMP)(4-HOMP) (NCS)2]2 (1), [Ni(3-HOMP)2(NCS)2(H2O)2] (2) and [Zn(4-HOMP)2(NCS)2] (4) where in all cases, the terminal NCS ion is coordinated to the metal centers through its N-donor atom. No NCS-bridging was observed in complex 1, but instead a bridging was performed via the hydroxyl and the N-pyridyl of a pair of 4-HOMP leading to long intradimer Cu Cu bond distance (7.908 Å) and hence very
weak antiferromagnetic coupling (J = 0.32 cm1). Also, in case of Cu(II) with l1,3-NCS-bridging similar magnetic behavior dominates [8,9,11–18]. The formation of mer-[Co(3-HOMP)3(N3)3]H2O (3) by the interaction of Co(II) salts with NaN3 in the presence of monodentate pyridyl or tridentate pyridyl (L) as coligand(s) have also been observed, where Co(II) was oxidized by air and octahedral fac-[Co(L)(N3)3] complexes were obtained [48]. In general, it should be interesting to explore the coordination chemistry of the three isomeric species of hydroxymethyl pyridine derivatives. While 2-, 3- and 4-HOMP compounds can act as monodentate ligands by coordinating metal ion only through the O-hydroxyl or the vast majority through N-pyridyl group [49–51,15] and moreover, they can serve as bridging ligands by simultaneous binding of the two N,O-donor atoms to metal ions [49,50,15,17], 2-HOMP is the only one that can generate chelated coordination compounds [52,53]. N-Bonding coordination has been observed in discrete complexes: [Cu(pdc)(3-HOMP)(H2O)] 2H2O [49], [Ni(pdc)(4-HOMP)(H2O)2]H2O [50] (pdc = pyridine2,6-dicarboxylate dianion), trans-[PtCl2(NH3)(3-HOMP)] and
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trans-[PtCl2(NH3)(4-HOMP)] [51], as well as in the Co(II) series [Co (NCS)2(4-HOMP)2X2], where X = 4-HOMP, H2O or EtOH [15]. Also, metal chelate complexes with 2-HOMP were obtained in a number of mononuclear compounds such as cis-[Ni(2-HOMP-j2N, O)2(H2O)2]Cl2 [52] and [Cu(2-HOMP-j2N,O)(NO3)2] [53]. In contrast, polymeric coordination compounds were reported in which metal ions are linked into chains by bridging HOMP ligands: [Co (NCS)2(l-4HOMP-jN,O)2]n4H2O, [Co(NCS)2(l-4HOMP-jN,O)2]n [15] [Cu(l-pdc)(l-4HOMP-jN,O)]n [50] [Cd(l-4HOMP-j2N:O)(4HOMP-jN)(l-NCS-j2N:S)(NCS-jN)]n [17] and [Cu(pdc)(l3HOMP-jN,O)]n [49] as well as polynuclear clusters with metal (II) ions and with mixed valence oxidation states of metals [54– 57] and in a few cases through the deprotonation of 2-HOMP ligand [57]. Acknowledgments F.A.M. thanks NAWI Graz for partial financial support and K. Gatterer, A. Huber and B. Baumgartner (TU-Graz) for assistance. S.S.M. acknowledges the financial support of this research by the Department of Chemistry-University of Louisiana at Lafayette. R. V. acknowledges the financial support from DGICT Project CTQ2015-63614-P. Appendix A. Supplementary data CCDC 1880866–1880869 contains the supplementary crystallographic data for 1–4. 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]. Supplementary data to this article can be found online at https://doi.org/10.1016/j.poly.2019.01.030. References [1] A. Escuer, J. Esteban, S.P. Perlepes, T.C. Stamatatos, Coord. Chem. Rev. 275 (2014) 87. [2] El. Shurdha, C.E. Moore, A.L. Rheingold, S.H. Lapidus, P.W. Stephens, A.M. Arif, J. S. Miller, Inorg Chem. 52 (2013) 10583. [3] (a) M. Rams, Z. Tomkowicz, T. Runecveski, M. Böhme, W. Plass, S. Suckert, J. Werner, I. Jess, C. Näther, Phys. Chem. Chem. Phys. 19 (2017) 3232; (b) J. Werner, M. Rams, Z. Tomkowicz, T. Runcevski, R.E. Dinnebier, S. Suckert, C. Näther, Inorg. Chem. 54 (2015) 2893; (c) J. Werner, Z. Tomkowic, M. Rams, S.G. Ebbinghaus, T. Neumann, C. Näther, Dalton Trans. 44 (2015) 14149; (d) S. Wöhlert, T. Fic, Z. Tomkowicz, S.G. Ebbinghaus, M. Rams, W. Haase, C. Näther, Inorg. Chem. 52 (2013) 12947; (e) S. Wöhlert, Z. Tomkowicz, M. Rams, S.G. Ebbinghaus, L. Fink, M.U. Schmidt, C. Näther, Inorg. Chem. 53 (2014) 8298. [4] A. S´witlicka, K. Czerwin´ska, B. Machura, M. Penkala, A. Bien´ko, D. Bien´ko, W. Zierkiewicz, CrystEngComm 18 (2016) 9042. [5] (a) J. Palion-Gazda, B. Machura, F. Lloret, M. Julve, Cryst. Growth Des. 15 (2015) 2380; _ J. Mrozin´ski, M. Julve, F. Lloret, A. Maslejova, W. Sawka(b) B. Zurowska, Dobrowolska, Inorg. Chem. 41 (2002) 1771. [6] A. Biswas, S. Mukherjee, S. Ghosh, C. Diaz, A. Ghosh, Inorg. Chem. Commun. 56 (2015) 108. [7] (a) S.S. Massoud, M.M. Henary, L. Maxwell, A. Martín, E. Ruiz, R. Vicente, R.C. Fischer, F.A. Mautner, New J. Chem. 42 (2018) 2627; (b) F.A. Mautner, M. Traber, R.C. Fischer, A. Torvisco, K. Reichmann, S. Speed, R. Vicente, S.S. Massoud, Polyhedron 154 (2018) 436; (c) F.R. Louka, S.S. Massoud, T.K. Haq, M. Koikawa, M. Mikuriya, M. Omote, R.C. Fischer, F.A. Mautner, Polyhedron 138 (2017) 177; (d) S.S. Massoud, F.R. Louka, Y.K. Obaid, R. Vicente, J. Ribas, R.C. Fischer, F.A. Mautner, Dalton Trans. 42 (2013) 3968. [8] (a) F.A. Mautner, R.C. Fischer, K. Reichmann, E. Gullett, K. Ashkar, S.S. Massoud, J. Mol. Struct. 1175 (2019) 1; (b) F.A. Mautner, C. Berger, R.C. Fischer, S.S. Massoud, Inorg. Chim. Acta 448 (2016) 34; (c) F.A. Mautner, C. Berger, R.C. Fischer, S.S. Massoud, Inorg. Chim. Acta 439 (2016) 69. [9] F.A. Mautner, C. Berger, R.C. Fisher, S.S. Massoud, Polyhedron 141 (2018) 17.
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Thiocyanato-metal(II) and azido-cobalt(III) complexes with hydroxymethylpyridines Franz A. Mautner a,⇑, Magdalena Traber a, Patricia Jantscher a, Roland C. Fischer b, Klaus Reichmann c, Ramon Vicente d, Noor Arafat e, Salah S. Massoud e a
Institut für Physikalische and Theoretische Chemie, Technische Universität Graz, A-8010 Graz, Austria Institut für Anorganische Chemie, Technische Universität Graz, A-8010 Graz, Austria Institut für Chemische Technologie von Materialien, Technische Universität Graz, A-8010 Graz, Austria d Department de Química Inorgànica, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain e Department of Chemistry, University of Louisiana at Lafayette, Lafayette, LA 70504 USA b c
a r t i c l e
i n f o
Article history: Received 25 November 2018 Accepted 12 January 2019 Available online 24 January 2019 Keywords: Isothiocyanate Copper Nickel Zinc Crystal structure
a b s t r a c t A dimeric [Cu(l-4-HOMP)(4-HOMP)(NCS)2]2 (1) and three discrete monomeric complexes [Ni(3-HOMP)2 (NCS)2(H2O)2] (2), [Co(3-HOMP)3(N3)3]H2O (3) and [Zn(4-HOMP)2(NCS)2] (4), (3-HOMP = 3hydroxymethylpyridine, 4-HOMP = 4-hydroxymethylpyridine) have been isolated and structurally characterized by IR, UV–Vis spectroscopy, XRPD, single crystal X-ray crystallography and Hirshfeld surface analysis as well as thermogravimetric analyses for complexes 1, 2 and 4. In dimeric complex 1 each penta-coordinated Cu2+ center is bridged through N,O-4-HOMP ligands, whereas metal ions in 2 and 3 are located in distorted octahedral geometry with mer-configuration in the azido complex 3. Distorted tetrahedral geometry is observed around Zn2+ in complex 4. The variable temperature magnetic susceptibility measurements of 1 showed very weak antiferromagnetic interaction. Ó 2019 Elsevier Ltd. All rights reserved.
1. Introduction Thiocyanato, NCS and azido, N 3 pseudo halides have been extensively used as bridging ligands in the construction of coordination polymers (CPs) and high nuclearity clusters with 3d metal ions and building block organic molecules [1–9]. The diversity of bonding modes of NCS and N 3 in metal complexes, which were summarized in some recent reports [1,7], led to the creation of compounds of potential applications in the field of luminescence [8] and molecular magnetism [1–7]. In bridging thiocyanato and azido compounds, the ions have the potential to mediate ferroand antiferro-magnetic coupling between the bridged paramagnetic metal ions resulting in interesting magnetic phenomena such as single molecule magnets (SMMs) and single chain magnets (SCMs) [1–7]. In discrete mononuclear thiocyanato- and azido-metal complexes, where NCS and N 3 are acting as terminal ligands only one coordination bonding site exists in the latter case, whereas in the NCS compounds two possible modes may be found due to the ambidentate nature of the ligand. Soft metal ions prefer
⇑ Corresponding author. E-mail address: [email protected] (F.A. Mautner). https://doi.org/10.1016/j.poly.2019.01.030 0277-5387/Ó 2019 Elsevier Ltd. All rights reserved.
binding through the S-site and hard metals prefer the N-site [10]. Although the nitrogen in NCS is categorized as at the borderline Lewis bases according to HSBA concept [10], most hard metals showed high preference to the N-site [11]. The metal ion’s preference to any of the coordination bonding sites in NCS complexes may change depending on a number of factors which include electronic nature and oxidation state of metal ion, the nature of the coordinated ancillary co-ligand(s) and the steric hindrance imposed by the coligand(s) surrounding the central metal ion [12]. The number of pseudohalide metal complexes with 3-hydroxymethylpyridine (3-HOMP) and 4-hydroxymethylpyridine (4HOMP) is quite limited due to lack of N,O-chelating modes in these species. In contrast, different azide bridging modes were observed in the polymeric chains of [M(L)y(N3)2]n (M = Cd [13] and Cu [7c], L = 3- or 4-hydroxymethylpyridine). Similarly bis-l1,5-dicyanamide (dca) bridges have been found in case of [M(4-HOMP)2(dca)2]n 1D systems (M = Co, Cu) [14]. Moreover, Näther et al. reported several series of mononuclear and polymeric isocyanate complexes with 4-HOMP co-ligand with Co [15], Ni [16] and a 3D network structure with Cd [17], in addition to a series of six Cd- and Zn-isocyanate complexes with 3-HOMP co-ligand [18]. Interestingly, the iron complex [Fe(3-HOMP)2(NCS)4] with the 3-HOMP co-ligands are N-coordinated to the Fe(III) ion, crystallizes
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with the protonation of 3-HOMP; HOMPH+ counter cations and neutral 3-HOMP solvent molecules [19]. In this paper, we explore the coordination chemistry of thiocyanato complexes with the borderline Lewis acids Cu2+, Ni2+ and Zn2+and azido-Co3+ complex with 3- and 4-hydroxymethyl- pyridine compounds namely: the dimeric [Cu(l-4-HOMP)(4-HOMP) (NCS)2]2 (1) and the monomeric species [Ni(3-HOMP)2(NCS)2(H2OH2O)2] (2), [Co(3-HOMP)3(N3)3]H2O (3) and [Zn(4-HOMP)2(NCS)2] (4).
2. Experimental
2.2.3. [Co(3-hydroxymethylpyridine)3(N3)3]H2O (3) A mixture of Co(NO3)26H2O (0.290, 1 mmol), NaN3 (0.13 g, 2 mmol) and 3-hydroxymethylpyridine (0.22 g, 2 mmol) are dissolved in 20 mL distilled H2O. The solution is stirred for 30 minutes at 75–80 °C, filtered while hot and then allowed to stand at room temperature (24–25 °C). The thin dark green well shaped needles, which were separated after 2 weeks, were collected by filtration (yield: 0.32 g, 90%). Anal. Calc. for C18H23CoN12O4 (530.41 g/mol): C, 40.8; H, 4.4; N, 31.7%. Found: C, 40.6; H, 4.3; N, 31.9%; (ATRIR, cm1): 3303 (s,br), 2008 (vs), 1606 (m), 1583 (w), 1478 (m), 1458 (w), 1431 (m), 1356 (mw), 1283 (s), 1203 (m), 1185 (m), 1110 (m), 1023 (s), 966 (m), 923 (m), 841 (w), 828 (w), 801 (m), 699 (w), 669 (m), 585 (m), 449 (w), 430 (w).
2.1. Materials and physical measurements 3-Hydroxymethylpyridine and 4-hydroxymethylpyridine were purchased from TCI and the other chemicals were of analytical grade quality. Infrared spectra of solid complexes were recorded on a Bruker Alpha P (platinum-ATR-cap) spectrometer. UV–Vis spectra were performed with a LS 950 Perkin-Elmer Lambda-spectrometer. Elemental microanalyses were carried out with an Elementar Vario EN3 analyser. Bulk phase purity of the title compounds was examined with a Bruker D8 Advance X-ray powder diffractometer (Figs S1–S4 in the supplementary materials section). A NETSCH STA 409 was used for thermoanalysis (heating rate: 10 °C/min, inert gas flow: 40 ml N2/min). Magnetic susceptibility measurements for 1 under 1 T magnetic field in the range 2–300 K and magnetization measurements in the field range of 1–4 T were performed with a Quantum Design MPMS-XL SQUID magnetometer at the Magnetochemistry Service of the University of Barcelona. All measurements were performed on polycrystalline samples. Pascal’s constants were used to estimate the diamagnetic corrections, which were subtracted from the experimental susceptibilities to give the corrected molar magnetic susceptibilities. Caution: Azido complexes and their salts are potentially explosive. Only small quantities should be handled with great care.
2.2. Synthesis of the complexes 2.2.1. [Cu(4-hydroxymethylpyridine)2(NCS)2]2 (1) A mixture of Cu(NO3)23H2O (0.48 g, 2 mmol), KSCN (0.39 g, 4 mmol) and 4-hydroxymethylpyridine (0.44 g, 4 mmol) were dissolved in 35 mL distilled H2O. The solution was heated up to 70 °C and stirred for 2 h. After filtration the green solution was stirred again for 20 min at the same temperature and then cooled down to RT. After a few hours small green crystals were obtained (yield: 0.54 g, 68%). Anal. Calc. for C14H14N4O2S2Cu (397.97 g/mol): C, 42.25; H, 3.55; N, 14.08; S, 16.11; Found: C, 42.19; H, 3.58; N, 14.15; S, 15.60%. IR (ATR, cm1): 3456 (w), 3275 (m), 2093 (vs), 1616 (m), 1561 (w), 1504 (w), 1423 (s), 1365 (m), 1195 (w), 1101 (vw), 1050 (m), 1019 (s), 801 (vs), 743 (w), 714 (w), 665 (w), 610 (m), 513 (w), 490 (m), 462 (m).
2.2.4. [Zn(4-hydroxymethylpyridine)2(SCN)2] (4) A mixture of ZnCl2 (0.13 g, 1 mmol), KSCN (0.19 g, 2 mmol) and g 4-hydroxymethylpyridine (0.22 g, 2 mmol) was dissolved in 15 mL distilled H2O. The solution was heated up to 55–60 °C and stirred for 1 h. After filtration, the clear solution was stirred again for 1 hour (50 °C) and then cooled down to room temperature. After 24 h clear colorless crystals were obtained (yield: 0.33 g, 83%). Anal. Calc. for C14H14N4O2S2Zn (399.81 g/mol): C, 42.06; H, 3.53; N, 14.01; S, 16.04%. Found: C, 41.84; H, 3.54; N, 14.00; S, 15.89%. IR (ATR, cm1): 3409 (s,br), 2075 (vs), 1621 (s), 1562 (w), 1508 (vw), 1452 (w), 1429 (m), 1340 (w), 1277 (w), 1224 (m), 1105 (w), 1034 (s), 949 (w), 807 (m), 722 (w), 657 (vw), 607 (m), 472 (s). 2.3. X-ray crystal structure analysis The X-ray single-crystal data of the four compounds were collected on a Bruker-AXS APEX CCD diffractometer at 100(2) K. The crystallographic data, conditions retained for the intensity data collection and some features of the structure refinements are listed in Table 1. The intensities were collected with Mo Ka radiation (k = 0.71073 Å). Data processing, Lorentz-polarization and absorption corrections were performed using APEX, and the SADABS computer programs [20]. The structures were solved by direct methods and refined by full-matrix least-squares methods on F2, using the SHELX program package [21]. All non-hydrogen atoms were refined anisotropically. The hydrogen atoms were located from difference Fourier maps, assigned with isotropic displacement factors and included in the final refinement cycles by use of geometrical constraints. In case of 1, a two-fold disorder with occupancy of 0.50 was observed for pyridine carbon atoms C (10)–C(13) and C(20)–C(23), respectively. Also in 3 for atoms of two-fold disordered hydroxymethyl groups split occupancies of 0.492(5)/0.508(2) for O(1)–C(6), 0.826(5)/0.174(5) for O(2)–C(12), 0.638(4)/0.362(4) for O(3)–C(18), respectively, were applied. The Molecular plots were performed with the Mercury program [22]. 3. Results and discussion 3.1. Synthesis of the complexes
2.2.2. [Ni(3-hydroxymethylpyridine)2(NCS)2(H2O)2] (2) Complex 2 was synthesized in a similar procedure as that described for 1 but with using NiSO46H2O (0.52 g, 2 mmol) and 3-hydroxymethylpyridine (0.44 g 4 mmol) instead. After 6 days at room temperature (approx. 25 °C) blue to turquoise regularshaped crystals were separated. These were collected by filtration (yield: 0.53 g, 62%). Anal. Calc. for C14H18N4NiO4S2 (429.15 g/mol): C, 39.2; H, 4.2; N, 13.1%. Found: C, 40.0; H, 4.0; N 13.4%; (ATR-IR, cm1): 3008 (w,br), mCN: 2098 (vs), 1733 (w), 1635 (w), 1481 (m), 1460 (s), 1432 (w), 1324 (w), 1188 (s), 1131 (m), 1059 (m), 936 (w), 807 (m), 756 (w), 706 (w), 649 (w), 608 (s), 458 (s).
Reactions of aqueous solutions containing the stoichiometric 1:2:2 molar ratios of Cu(NO3)23H2O, NiSO46H2O or ZnCl2, KNCS and 3- or 4-hydroxymethylpyridine afforded the dimeric [Cu(l4-HOMP)(4-HOMP)(NCS)2]2 (1) as well as the discrete monomeric complexes [Ni(3-HOMP)2(NCS)2(H2O)2] (2) and [Zn(4-HOMP)2 (NCS)2] (4) in moderate to high yields with good quality single crystals. Analogous reaction of an aqueous solution of Co(NO3)26H2O with two equivalents of 3-hydroxymethylpyridine and in the presence two equivalents of NaN3 yielded dark green needles of [Co(3-HOMP)3(N3)3]H2O (3), where Co2+ was slowly oxidized by
F.A. Mautner et al. / Polyhedron 161 (2019) 309–316 Table 1 Crystallographic data and processing parameters for 1–4. Compound
1
2
Empirical formula Formula mass System Space group
C28H28Cu2N8O4S4 795.92 monoclinic P21/c
C14H18N4NiO4S2 429.15 triclinic
a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z T (K) l (mm1) Dcalc (Mg/m3) Crystal size (mm) h max (°) Data collected Unique reflections (Rint) Parameters Goodness-of-Fit (GOF) on F2 R1/wR2 (all data) Residual extrema (e/Å3)
10.9582(14) 19.6859(18) 8.0786(12) 90 111.469(2) 90 1621.8(4) 2 100(2) 1.617 1.630 0.26 0.20 0.13 25.284 11 792 2935/0.0626 250 1.374 0.0880/0.1735 0.99 and 0.73
Compound Empirical formula Formula mass System Space group
3 C18H23CoN12O4 530.41 Triclinic
a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z T (K) l (mm1) Dcalc (Mg/m3) Crystal size (mm) h max (°) Data collected Unique reflections (Rint) Parameters Goodness-of-Fit (GOF) on F2 R1/wR2 (all data) Residual extrema (e/Å3)
P1 9.5389(7) 10.1934(8) 12.2606(9) 96.070(3) 108.146(3) 93.517(4) 1120.88(15) 2 100(2) 0.820 1.572 0.23 0.16 0.11 30.089 68 273 6570/0.0283 367 1.063 0.0337/0.0904 1.16 and 0.52
P1 7.6565(8) 8.6363(11) 8.7184(11) 67.363(2) 65.653(2) 66.934(2) 465.76(10) 1 100(2) 1.291 1.530 0.38 0.28 0.15 26.324 3743 1866/0.0223 124 1.092 0.0235/0.0612 0.25 and 0.28 4 C14H14N4O2S2Zn 399.18 Monoclinic P2/n 18.3490(15) 5.0296(3) 18.8817(17) 90 95.910(4) 90 1733.3(2) 4 100(2) 1.670 1.532 0.27 0.19 0.11 26.328 12 908 3529/0.0350 215 1.114 0.0429/0.0979 0.83 and 0.29
air upon standing at room temperature. The purity of the synthesized complexes was examined by elemental microanalyses and their bulk phase purity by XRPD. The complexes were also investigated by IR and UV–Vis spectroscopy, and Hirshfeld surface calculations as well as thermogravimetric analysis for 1, 2 and 4. 3.2. IR and UV–Vis spectra of the complexes The IR spectra of the complexes under investigation display some general characteristic features. In addition of the vibrations of the methylpyridine moiety, very strong absorption bands observed at 2093 cm1 (1), 2098 cm1 (2), and 2075 cm1 (4) are due to the asymmetric stretching frequencies of the coordinated NCS ligands. The appearance of mas(NCS) at a frequency value <3100 cm1 is more consistent with N-NCS bonding [11], whereas complex 3 shows the very strong mas(N3) vibration of the azide groups at 2008 cm1 [7]. The four title complexes display medium to strong broad bands above 3000 cm1, respectively due to m(OH) of the aqua ligand, water of crystallization and/or the hydroxyl O– H stretching vibration of hydroxymethylpyridine molecules [14]. The UV–Vis spectrum of solid copper(II) complex 1 displays a broad absorption band centered around 612 nm accompanied with
311
a low-energy shoulder at k > 800 nm. This feature is consistent with five-coordinate Cu(II) complexes with square pyramidal geometry (SP) [7,8c]. The UV–Vis spectrum of solid nickel(II) complex 2 displays three maxima at 372, 606 and 973 nm. These spec3 tral bands are assigned to the electronic transitions 3T1g(P) A2g, 3 3 3 T1g(F) A2g and 3T2g A2g, respectively for Ni(II) in octahedral environment [23–25]. The UV–Vis spectrum of solid cobalt(III) complex 3 shows a broad absorption band centered at 610 nm which corresponds to the electronic transition 5E T2 of octahedral Co(III) in weak ligand field environment [23–25]. 3.3. Description of the crystal structures 3.3.1. [Cu(l-4-HOMP)(4-HOMP)(NCS)2]2 (1) A perspective view of 1 is given in Fig. 1, a packing view is in Fig. S5 in the supplementary materials section, and selected bond parameters are summarized in Table 2. The Cu(1) metal center is penta-coordinated by N(1) and N(2) atoms of two terminal isothiocyanato anions, by N(3) of a terminal 4-hydroxymethylpyridine molecule, further by O(2) and N(40 ) atoms of two l(N,O)-bridging 4-hydroxymethylpyridine molecules, which connect Cu(1) and Cu(10 ) polyhedra to form centrosymmetric dinuclear units. The CuN4O chromophore may be described as slightly distorted square pyramid (SP) with a s-value of 0.03 [s-values of 1 and 0 refer to ideal geometries of trigonal bipyramid (TBP) and square pyramid (SP), respectively] [26]. The apical site is occupied by O(2) [Cu (1)-O(2) = 2.379(5) Å]. The basal Cu–N bond distances are in the range from 1.954(6) to 2.041(6) Å. The terminal isothiocyanate anions have following bond parameters: N–C: 1.138(8) and 1.156 (9) Å, C–S: 1.644(7) and 1.637(8) Å, Cu–N–C: 170.8(6) and 169.0 (6)°, N–C–S: 178.0(7) and 178.7(7)°. The Cu(1) Cu(10 ) distance is 7.9083(18) Å and the shortest inter-dinuclear metal–metal separation is 5.8666(16) Å. Along the c-axis the Cu(1) S(200 ) [(00 ): x, y,1 z] separation is 3.117(2) Å. Hydrogen bonds of type O–H S between hydroxy-groups of pyridine derivative ligands and adjacent non-coordinated S atoms of terminal isothiocyanate anions form a supramolecular 2D system oriented along the b- and c-axis of the monoclinic unit cell [O(1)–H(91) S(2#1) = 155(3)°, O(1) S (2#1) = 3.454(7) Å; O(2)–H(92) S(1#2) = 172(4)°, O(2) S(1#2) = 3.168(5) Å; (#1): x,1/2 y,1/2 + z; (#2): x,1/2 y,1/2 + z]. In the crystal structures of [M(4-HOMP)2(NCS)2]n (M = Co [15], Ni [16]) the octahedrally coordinated metal(II) centers are linked into dimers by pairs of l(N,S)-bridging NCS anions and are further connected into chains by the l(N,O)-bridging 4-hydroxymethylpyridine molecules. 3.3.2. [Ni(3-HOMP)2(NCS)2(H2O)2] (2) A perspective view of 2, together with the atom numbering scheme is given in Fig. 2. The crystal structure of 2 consists of neutral mononuclear Ni(II) complexes. The Ni(1) atom is located at the
Fig. 1. Perspective view of 1. Symmetry code: (0 ) 1 x,y,1 z.
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Table 2 Selected bond lengths (Å) and angles (°) for compound 1–4. Compound 1 Cu(1)–N(1) Cu(1)–N(2) Cu(1)–N(3) N(1)–C(1) N(2)–C(2) N(2)–Cu(1)–N(1) N(1)–Cu(1)–N(3) N(1)–Cu(1)–N(40 ) N(2)–Cu(1)–O(2) N(3)–Cu(1)–O(2) Cu(1)–N(1)–C(1) Cu(1)–N(2)–C(2)
1.973(6) 1.954(6) 2.028(6) 1.138(8) 1.156(9) 177.6(3) 88.9(2) 90.5(2) 93.0(2) 92.3(2) 170.8(6) 169.0(6)
Compound 2 Ni(1)–N(1) Ni(1)–O(2) C(7)–S(1) N(1)–Ni(1)–N(10 ) N(1)–Ni(1)–O(2) Ni(1)–N(3)–C(7)
2.1177(12) 2.0724(11) 1.6439(15) 180 91.15(4) 160.92(12)
Compound 3 Co(1)–N(1) Co(1)–N(7) Co(1)–N(11) N(1)–N(2) N(4)–N(5) N(7)–N(8) N(1)–Co(1)–N(11) N(4)–Co(1)–N(7) Co(1)–N(4)–N(5) N(1)–N(2)–N(3) N(7)–N(8)–N(9) Compound 4 Zn(1)–N(10 ) Zn(1)–N(3) N(1)–C(1) N(2)–C(2) N(1)–Zn(1)–N(10 ) N(10 )–Zn(1)–N(3) N(10 )–Zn(1)–N(30 ) N(3)–Zn(1)–N(30 ) Zn(1)–N(1)–C(1) Zn(2)–N(2)–C(2)
Cu(1)–N(40 ) Cu(1)–O(2) S(1)–C(1) S(2)–C(2)
2.041(6) 2.379(5) 1.644(7) 1.637(8)
N(2)–Cu(1)–N(3) N(2)–Cu(1)–N(40 ) N(3)–Cu(1)–N(40 ) N(1)–Cu(1)–O(2) N(4)–Cu(1)–O(20 ) N(1)–C(1)–S(1) N(2)–C(2)–S(2)
88.8(2) 91.8(3) 179.4(3) 87.8(2) 87.7(2) 178.0(7) 178.7(7)
Ni(1)–N(3) N(3)–C(7)
2.0454(13) 1.156(2)
N(3)–Ni(1)–O(20 ) N(30 )–Ni(1)–N(1) N(3)–C(7)–S(1)
91.07(5) 90.40(5) 178.99(13)
1.9448(13) 1.9571(13) 1.9936(13) 1.200(2) 1.1988(18) 1.200(2) 175.53(5) 176.58(5) 123.63(10) 176.11(18) 175.95(17)
Co(1)–N(4) Co(1)–N(10) Co(1)–N(12) N(2)–N(3) N(5)–N(6) N(8)–N(9) N(10)–Co(1)–N(12) Co(1)–N(1)–N(2) Co(1)–N(7)–N(8) N(4)–N(5)–N(6)
1.9628(12) 1.9695(12) 1.9607(12) 1.155(2) 1.1561(19) 1.151(2) 178.75(5) 121.14(11) 121.20(11) 176.14(16)
1.942(2) 2.018(2) 1.158(4) 1.159(4) 121.03(15) 103.53(9) 108.81(9) 111.16(13) 174.3(2) 169.0(2)
Zn(2)–N(200 ) Zn(2)–N(4) S(1)–C(1) S(2)–C(2) N(2)–Zn(2)–N(200 ) N(200 )–Zn(2)–N(4) N(200 )–Zn(2)–N(400 ) N(4)–Zn(2)–N(400 ) N(1)–C(1)–S(1) N(2)–C(2)–S(2)
1.939(2) 2.019(2) 1.627(3) 1.627(3) 124.27(15) 105.24(9) 105.90(10) 109.91(13) 177.6(3) 177.7(3)
minal N-coordinated NCS- anions are: Ni(1)–N(3)–C(7) = 160.93 (12), N(3)–C(7)–S(1) = 178.98(13)°, N(3)–C(7) = 1.156(2), C(7)–S (1) = 1.6439(15) Å. Further selected bond lengths and angles are listed in Table 2. The shortest metal–metal separation is 7.6565 (10) Å. A supramolecular three-dimensional network is formed by hydrogen bonds of type O–H S and O–H O (Fig. S6). [O(2)– H(91) S(1#1) = 158°, O(2) S(1#1) = 3.2535(16) Å; O(1)–H(92) S(1#2) = 146°, O(1) S(1#2) = 3.3309(14) Å; O(2)–H(90) O(1#3) = 177°, O(2) O(1#3) = 2.7320(19) Å; (#1): x,1 + y,z; (#2): 1 + x, y,1 + z; (#3): 2 x,y,2 z]. Analogous [Ni(py-R)2(NCS)2(H2O)] complexes with the following py-R (pyridine derivative ligand) have been structurally characterized: nicotinamide [27], 2,5-bis (4-pyridinyl)-1,3,4-thiadiazole [28], 5-nitroquinoline [29], pyridine-4-carboxylic acid [30,31], 1-(pyridin-4-yl)ethanone [32], 2chloropyridine [33], 3-methylpyridine [34], 4-hydroxymethylpyridine [16], 4-aminopyridine [35]. 3.3.3. [Co(3-HOMP)3(N3)3]H2O (3) A perspective view of 3, together with the atom numbering scheme is given in Fig. 3, a packing view in Fig. S7 and selected bond lengths and bond angles are given in Table 2. The crystal structure of 3 consists of neutral mononuclear [Co(3-HOMP)3(N3)3] complexes and lattice water molecules. The Co(1) center is octahedrally coordinated by six N-donor atoms (three of them from Npyridyl 3-HOMP molecules, and remaining three from terminal azido anions) in a mer-conformation. The Co(1)–N bond distances are in the range from 1.9448(13) to 1.9936(13) Å. The transoid N–Co(1)–N bond angles vary from 175.53(5)° to 178.75(5)° and the cisoid N–Co(1)–N bond angles are in the range from 87.29 (5)° to 93.66(5)°. The bond parameters of the terminal azido groups
Symmetry codes: for 1: (0 ) 1 x,y,1 z; for 2: (0 ) 2 x,1 y,1 z; for 4: (0 ): 3/2 x,y,1/2 z; (00 ): 3/2 x,y,3/2 z.
inversion center. It is six-coordinated by N(1), N(10 ) of two 3-hydroxymethylpyridine molecules, N(3) and N(30 ) of two isothiocyanato anions and O(2) and O(20 ) of two aqua ligands. The NiN4O2 chromophore may be described as distorted octahedron with Ni (1)–O/N bond distances in the range from 2.0454(13) to 2.1177(12) Å. The cisoid N–Ni(1)–O and N–Ni(1)–N bond angles are in the range from 88.85(4) to 91.15(4)°. The bond parameters of the ter-
Fig. 2. Perspective view of 2. Symmetry code: (0 ) 2 x, 1 y, 1 z.
Fig. 3. Perspective view of 3.
Fig. 4. The two crystallographic independent Zn(II) polyhedra of 4. Symmetry codes: (0 ): 3/2 x,y,1/2 z; (00 ): 3/2 x,y,3/2 z.
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Fig. 5. TG curves of 1 (top), 2 (middle) and 4 (bottom).
are: Co(1)–N–N: from 121.20(11) to 123.63(10)°; N–N–N: from 175.95(17) to 176.14(16)°; N(a)–N(b): from 1.1988(18) to 1.200 (2) Å; N(b)–N(c): from 1.151(2) to 1.1561(19) Å [with N(a) ligated to Co(1)]. The shortest metal–metal separation is 6.4581(6) Å. Oxy-
gen donor atoms of the two-fold disordered hydroxymethyl groups and of ordered non-coordinated water molecules form hydrogen bonds of type O–H O and O–H N: [O(3a)–H(3a) O(4#1) = 161°, O(3a) O(4#1) = 2.806(4) Å; O(4)–H(41) N(6#2) = 175°, O
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3.4. Thermoanaytical behavior
Fig. 6. vMT plot vs. T for compound 1.
(4) N(6#2) = 2.891(3) Å; O(4)–H(42) O(2a) = 113°, O(4) O(2a) = 2.703(3) Å; (#1): x,1 + y,z; (#2): x,y,1 z]. As far as we know, only six monomeric Co(III) complexes of composition [Co(pyR)3(N3)3] have been reported with following py-R: tris(2-pyridyl) methylamine [36], mer-configuration for py [37], 3,4- and 3,5dimethylpyridine [38], 4-methylpyridine [39], whereas fac-configuration was observed only once for a complex containing py and 2,20 -bipy simultaneously [40].
3.3.4. [Zn(4-hydroxymethylpyridine)2(NCS)2] (4) The crystal structure of 4 (perspective view is shown in Fig. 4, a packing view in Fig. S4 and selected bond parameters are listed in Table 2) consists of two crystallographically independent mononuclear neutral Zn(II) complexes. Each Zn(II) is tetrahedrally coordinated by N atoms of two terminal isothiocyanato anions, and by N atoms of two neutral 4-hydroxymethylpyridine molecules. The Zn–N bond distances are in the range from 1.942(2) to 2.018(2) Å, and the bond angles within the ZnN4 tetrahedron vary from 103.53(9)° to 124.3(2)°. The bond parameters of terminal N-coordianted NCS anions are: Zn–N–C = 169.0(2) and 174.3(2)°, N–C– S = 177.7(3)°, N–C = 1.159(4) and 1.158(4) A, C–S = 1.627(3) Å. The shortest metal–metal separation is 5.0296(8) Å. Hydrogen bonds of type O–H S form a supramolecular 2D system [O(1)–H (1) S(2#1)(#1: 3/2 x,1 + y,3/2 z) = 162(4)°, O(1) S(2#1) = 3.265(3) Å; O(2)–H(2) S(1#2)(#2: x,2 + y,z) = 171(4)°, O(1) S (2#1) = 3.239(3) Å]. A CSD search (version 5.39, updates Aug 2018) for monomeric [Zn(py-R)2(NCS)2] with tetrahedrally coordinated Zn(II) centers revealed 40 hits. Compilation of the bond parameters for 38 of the reported ZnN4 coordination figures gave the following results: Zn–N(NCS): from 1.911 to 1.963 Å, mean 1.934 Å, Zn–N(py) from 1.991 to 2.059 Å, mean 2.029 Å; N(NCS)– Zn–N(NCS): from 105.95° to 125.67°, mean 117.86°, N(py)–Zn–N(py): from 102.38 to 117.17°, mean 109.92°. Thus the Zn–N(py) bonds are by 0.078 Å longer, and the N(py)–Zn–N(py) angles by 12.11° smaller than the corresponding bond parameters of the N-terminal isothiocyanate anions. In case of the complex with 3-hydroxymethylpyridine (refcode: ZEMNAJ [18]) ‘‘inverted” bond parameters are observed: 1.988 vs. 1.966 Å and 109.41 vs. 109.95°. The sterical hindrance of the chelating bis-pyridyl ligands 1,10phenanthroline-N,N0 (refcode: TOBGIB [41]) and 6-bromo-N(pyridin-2-yl)pyridin-2-amine (refcode: FUZXIJ [42]) leads to much smaller N(py)-Zn-N(py) chelating angles of 81.62° and 94.66°, respectively. Interestingly, only the complex with isoquinoline ligands (refcode EFOXOO [43]) forms two crystallographically independent ZnN4 polyhedra and crystallizes as 4 in the space group P2/n.
The thermogravimetric heating curves of compounds 1, 2 and 4 are given in Fig. 5. Compounds 1 and 4 show the following four steps of weight loss (Dm): (1): 32.85% (from 102 to 238 °C), 25.56% (from 238 to 297 °C), 9.96% (from 297 to 438 °C), and 4.49% (from 438 to 980 °C); and (4): 24.10% (from 135 to 270 °C), 27.32% (from 270 to 359 °C), 6.84% (from 359 to 467 °C), and 8.49% (from 467 to 980 °C). The first two steps of weight loss in 1 and 4 may be attributed to the release of the hydroxymethylpyridine molecules, Compound 2 shows the following three steps of weight loss (Dm): 7.26% (from 85 to 170 °C), 57.68% (from 170 to 434 °C) and 7.94% (from 434 to 980 °C). In this case, the first two steps may be attributed to the loss of the two aqua ligands (Calcd: weight loss: 8.40%) followed by the release of the two 3-HOMP ligands (Calcd: weight loss: 50.86%). 3.5. Magnetic properties of [Cu(l-4-HOMP)(4-HOMP)(NCS)2]2 (1) The plot of vMT vs. T for compound 1 is shown in Fig. 6. Compound 1 shows a vMT value of 0.87 cm3 mol1 K at room temperature. This value is slightly higher than that expected for two uncoupled S = 1/2 spins (0.75 cm3 mol1 K, g = 2.0). Upon cooling the vMT values are practically constant, decreasing only from T < 25 K to a value of 0.78 cm3 mol1 K at 2 K. The vM values increase on cooling from 2.9 103 cm3 mol1 at 300 K without a maximum. This behavior indicates slight antiferromagnetic coupling or un-coupled dinuclear system. Based on the situation, the experimental magnetic data for 1 have been fitted using the Bleaˆ = JSˆA.SˆB with ney-Bowers expression based on the Hamiltonian H SA = SB = 1/2 (Eq. (1)).
vM ¼ 2Ng2 l2B =kT ½3 þ expðJ=kT Þ1
ð1Þ
Least-squares fitting on all experimental data led to the following parameters: J = 0.32(2) cm1, g = 2.13(1). 3.6. Hirshfeld surface analyses With the Hirshfeld surface calculations [44,45] it is possible to obtain three-dimensional pictures of close contacts in a crystal. The Hirshfeld surfaces of complexes 1–4 are presented in Figs. S9–S11, giving surfaces that have been mapped over dnorm, shape index and curvedness. A very useful supplement of the Hirshfeld surface calculations are the 2D fingerprint plots [45–47], giving a quantitative analysis of the nature and type of intermolecular interactions between complex molecules. With the 2D fingerprint plots it is possible to separate various intermolecular interactions to particular atom pair close contacts. E.g. the H O/O H interactions are represented by a spike in the 2D fingerprint plots [H O acceptor interactions as a spike in the bottom right region, O H donor interactions as a spike in the bottom left region], whereas in a full 2D fingerprint plot all possible contributions from different interactions are overlapped. The main contributions in the fingerprint plots are given in Figs. 7 and 8. For 1 (Fig. 7, top row): H C/C H 15.2%; H H 34.1%; H O/O H 6.0%; H S/S H 32.3% and C C 3.1%, remaining 9.1%. For 2 (Fig. 7, second row): H C/C H 17.0%; H H 30.2%; H O/O H 12.5%; H S/S H 27.4% and C C 5.3%, remaining 7.6%. For 4 (Fig. 7, third row): H C/C H 17.2%; H H 28.9%; H O/O H 5.9%; H S/S H 29.0% and C N/N C 8.7%, remaining 10.3%. For the azido complex 3 (Fig. 8: H C/C H 7.4%; H H 36.7%; H O/O H 14.9%; H N/N H 30.9% and C N/N C 5.4%, remaining 4.7%. For the isothiocyanato complexes the H S/S H contributions are in the range from 27.4 to 32.3%, whereas the
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Fig. 7. 2D fingerprint plots for 1 (first row), 2 (second row), and 4 (third row).
Fig. 8. 2D fingerprint plots for 3.
H O/O O are much lower from 5.9 to 12.5%, reflecting the dominance of the O–H S hydrogen bonds. In the azido complex 3 the O–H N hydrogen bonds dominate as the H N/N H contacts are approx. twice as large as the O H/H O contacts.
4. Conclusions To conclude, the interaction of the borderline Lewis acids Cu2+, Ni2+ and Zn2+ with ambidentate Lewis bases with hard/soft donor sites such as NCS- in the presence of 3- and 4-hydroxymethyl- pyridine as coligands to form mono- or di-nuclear metal complexes results in the formation of species [Cu(l-4-HOMP)(4-HOMP) (NCS)2]2 (1), [Ni(3-HOMP)2(NCS)2(H2O)2] (2) and [Zn(4-HOMP)2(NCS)2] (4) where in all cases, the terminal NCS ion is coordinated to the metal centers through its N-donor atom. No NCS-bridging was observed in complex 1, but instead a bridging was performed via the hydroxyl and the N-pyridyl of a pair of 4-HOMP leading to long intradimer Cu Cu bond distance (7.908 Å) and hence very
weak antiferromagnetic coupling (J = 0.32 cm1). Also, in case of Cu(II) with l1,3-NCS-bridging similar magnetic behavior dominates [8,9,11–18]. The formation of mer-[Co(3-HOMP)3(N3)3]H2O (3) by the interaction of Co(II) salts with NaN3 in the presence of monodentate pyridyl or tridentate pyridyl (L) as coligand(s) have also been observed, where Co(II) was oxidized by air and octahedral fac-[Co(L)(N3)3] complexes were obtained [48]. In general, it should be interesting to explore the coordination chemistry of the three isomeric species of hydroxymethyl pyridine derivatives. While 2-, 3- and 4-HOMP compounds can act as monodentate ligands by coordinating metal ion only through the O-hydroxyl or the vast majority through N-pyridyl group [49–51,15] and moreover, they can serve as bridging ligands by simultaneous binding of the two N,O-donor atoms to metal ions [49,50,15,17], 2-HOMP is the only one that can generate chelated coordination compounds [52,53]. N-Bonding coordination has been observed in discrete complexes: [Cu(pdc)(3-HOMP)(H2O)] 2H2O [49], [Ni(pdc)(4-HOMP)(H2O)2]H2O [50] (pdc = pyridine2,6-dicarboxylate dianion), trans-[PtCl2(NH3)(3-HOMP)] and
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trans-[PtCl2(NH3)(4-HOMP)] [51], as well as in the Co(II) series [Co (NCS)2(4-HOMP)2X2], where X = 4-HOMP, H2O or EtOH [15]. Also, metal chelate complexes with 2-HOMP were obtained in a number of mononuclear compounds such as cis-[Ni(2-HOMP-j2N, O)2(H2O)2]Cl2 [52] and [Cu(2-HOMP-j2N,O)(NO3)2] [53]. In contrast, polymeric coordination compounds were reported in which metal ions are linked into chains by bridging HOMP ligands: [Co (NCS)2(l-4HOMP-jN,O)2]n4H2O, [Co(NCS)2(l-4HOMP-jN,O)2]n [15] [Cu(l-pdc)(l-4HOMP-jN,O)]n [50] [Cd(l-4HOMP-j2N:O)(4HOMP-jN)(l-NCS-j2N:S)(NCS-jN)]n [17] and [Cu(pdc)(l3HOMP-jN,O)]n [49] as well as polynuclear clusters with metal (II) ions and with mixed valence oxidation states of metals [54– 57] and in a few cases through the deprotonation of 2-HOMP ligand [57]. Acknowledgments F.A.M. thanks NAWI Graz for partial financial support and K. Gatterer, A. Huber and B. Baumgartner (TU-Graz) for assistance. S.S.M. acknowledges the financial support of this research by the Department of Chemistry-University of Louisiana at Lafayette. R. V. acknowledges the financial support from DGICT Project CTQ2015-63614-P. Appendix A. Supplementary data CCDC 1880866–1880869 contains the supplementary crystallographic data for 1–4. 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]. Supplementary data to this article can be found online at https://doi.org/10.1016/j.poly.2019.01.030. References [1] A. Escuer, J. Esteban, S.P. Perlepes, T.C. Stamatatos, Coord. Chem. Rev. 275 (2014) 87. [2] El. Shurdha, C.E. Moore, A.L. Rheingold, S.H. Lapidus, P.W. Stephens, A.M. Arif, J. S. Miller, Inorg Chem. 52 (2013) 10583. [3] (a) M. Rams, Z. Tomkowicz, T. Runecveski, M. Böhme, W. Plass, S. Suckert, J. Werner, I. Jess, C. Näther, Phys. Chem. Chem. Phys. 19 (2017) 3232; (b) J. Werner, M. Rams, Z. Tomkowicz, T. Runcevski, R.E. Dinnebier, S. Suckert, C. Näther, Inorg. Chem. 54 (2015) 2893; (c) J. Werner, Z. Tomkowic, M. Rams, S.G. Ebbinghaus, T. Neumann, C. Näther, Dalton Trans. 44 (2015) 14149; (d) S. Wöhlert, T. Fic, Z. Tomkowicz, S.G. Ebbinghaus, M. Rams, W. Haase, C. Näther, Inorg. Chem. 52 (2013) 12947; (e) S. Wöhlert, Z. Tomkowicz, M. Rams, S.G. Ebbinghaus, L. Fink, M.U. Schmidt, C. Näther, Inorg. Chem. 53 (2014) 8298. [4] A. S´witlicka, K. Czerwin´ska, B. Machura, M. Penkala, A. Bien´ko, D. Bien´ko, W. Zierkiewicz, CrystEngComm 18 (2016) 9042. [5] (a) J. Palion-Gazda, B. Machura, F. Lloret, M. Julve, Cryst. Growth Des. 15 (2015) 2380; _ J. Mrozin´ski, M. Julve, F. Lloret, A. Maslejova, W. Sawka(b) B. Zurowska, Dobrowolska, Inorg. Chem. 41 (2002) 1771. [6] A. Biswas, S. Mukherjee, S. Ghosh, C. Diaz, A. Ghosh, Inorg. Chem. Commun. 56 (2015) 108. [7] (a) S.S. Massoud, M.M. Henary, L. Maxwell, A. Martín, E. Ruiz, R. Vicente, R.C. Fischer, F.A. Mautner, New J. Chem. 42 (2018) 2627; (b) F.A. Mautner, M. Traber, R.C. Fischer, A. Torvisco, K. Reichmann, S. Speed, R. Vicente, S.S. Massoud, Polyhedron 154 (2018) 436; (c) F.R. Louka, S.S. Massoud, T.K. Haq, M. Koikawa, M. Mikuriya, M. Omote, R.C. Fischer, F.A. Mautner, Polyhedron 138 (2017) 177; (d) S.S. Massoud, F.R. Louka, Y.K. Obaid, R. Vicente, J. Ribas, R.C. Fischer, F.A. Mautner, Dalton Trans. 42 (2013) 3968. [8] (a) F.A. Mautner, R.C. Fischer, K. Reichmann, E. Gullett, K. Ashkar, S.S. Massoud, J. Mol. Struct. 1175 (2019) 1; (b) F.A. Mautner, C. Berger, R.C. Fischer, S.S. Massoud, Inorg. Chim. Acta 448 (2016) 34; (c) F.A. Mautner, C. Berger, R.C. Fischer, S.S. Massoud, Inorg. Chim. Acta 439 (2016) 69. [9] F.A. Mautner, C. Berger, R.C. Fisher, S.S. Massoud, Polyhedron 141 (2018) 17.
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