Preparation and Characterization of Anion-Dependent Octahedral Nickel(II) Geometric Isomers

Experimental

Materials and Measurements. All chemicals used in the synthesis were of reagent grade and used without further purification. N-(2-pyridylmethyl)-iminodiethanol (H2pmide) was prepared according to literature procedures.16 UV/Vis absorption spectra were recorded with a SCINCO S-2100 spectrophotometer. Infrared spectra were recorded with a Thermo Fisher Scientific IR200 spectrophotometer (± 1 cm−1) using KBr disk. Elemental analyses were carried out using a Fissons/Carlo Erba EA1108 instrument. X-ray powder diffraction (XRPD) patterns were measured on a Bruker AXS D2 Phaser X-ray Diffractometer with increments of degree and time step of 0.02° and 0.2 sec/step in 2𝛳. Luminescence spectra were obtained with a SINCO FS-2 fluorescence spectrometer.

Preparation of 1. To an MeCN solution (2 mL) of H2pmide (100 mg, 0.51 mmol) was added an MeCN/MeOH (v/v, 2:1) mixture solution (3 mL) of Ni(NO3)2·6H2O (74 mg, 0.25 mmol), and the color became light violet, and the solution was stirred for 30 min at room temperature. After filtrating, pink crystals were obtained by slow diffusion of diethyl ether into the mixture solution of 1, collected by filtration, and washed with acetonitrile and dried in air. Yield: 129 mg (88%). FT-IR (KBr, cm−1): 3392, 3085, 2975, 1609, 1384, 1068, 1027, 769. UV/Vis (diffuse reflectance spectrum):λmax = 264, 308 (sh), 544, 917 nm. Anal. calcd for C20H32N6NiO10: C, 41.76; H, 5.61; N, 14.61. Found: C, 41.60; H, 5.64; N, 14.37.

Preparation of 2. This complex was obtained as blue crystals in a manner similar to the synthesis of 1 except that NiCl2·6H2O (61 mg, 0.25 mmol) instead of Ni(NO3)2·6H2O was used. Yield: 122 mg (91%). FT-IR (KBr, cm−1): 3357, 3046, 2968, 1609, 1433, 1066, 1028, 780. UV/Vis (diffuse reflectance spectrum):λmax = 264, 304 (sh), 360 (sh), 579, 796 (sh, forbidden), 989 nm. Anal. calcd for C20H32Cl2N4NiO4: C, 46.01; H, 6.18; N,10.73. Found: C, 45.86; H, 6.24; N, 10.79.

Crystal Structure Determination. Single crystals of 1 and 2 were coated with paratone-N oil and the diffraction data measured at 100(2) K with synchrotron radiation (λ = 0.70000 Å) on an ADSC Quantum-210 detector at 2D SMC with a silicon (111) double crystal monochromator (DCM) at the Pohang Accelerator Laboratory, Korea. The ADSC Q210 ADX program17 was used for data collection (detector distance is 63 mm, omega scan; Δω= 1°, exposure time is 1 sec per frame) and HKL3000sm (Ver. 703r)18 was used for cell refinement, reduction and absorption correction. The crystal structures of 1 and 2 were solved by direct methods,19 and refined by full-matrix least-squares refinement using the SHELXL-97 computer program.20 The positions of all nonhydrogen atoms were refined with anisotropic displacement factors. All hydrogen atoms were placed using a riding model, and their positions were constrained relative to their parent atoms using the appropriate HFIX command in SHELXL-97, except the hydrogen atoms of coordinated hydroxyl groups. The crystallographic data and the result of refinements of 1-2 are summarized in Table 2.

Table 2.aR1 = ∑||Fo| − |Fc||/∑ |Fo|. bwR2 = [∑w(Fo2 −Fc2)2/∑w(Fo2)2]1/2.