Synthesis, Crystal Structure And Photo-electric Property Of A Series Of Co-M Homometallic/Heterometallic Polynuclear Coordination Polymers

Fourteen coordination polymers have been synthesized by the reaction of Co(II), Fe(II), Ni(II) and Cd(II) ion with succinic acid, benzene-1,3,5-tricarboxylic acid and phthalic acid under hydrothermal conditions. Their structures had been determined by X-ray single crystal diffraction. The formulas of coordination polymers are listed as follows:ⅰA series of Co(II) homometallic polynuclear coordination polymers (1)⁷ (1)[Co7( suc )4( OH )6( H₂O )₃·8H₂O]_n (2)[Co₄( suc )₃( OH )₂( H₂O )₂·2H₂O]_n (3)[Co( suc )]_n (4)[Co( suc )0.5( Im )]_n (5)[Co( phth )( Imh )₂]_n (6)[Co( phth )( Pz )₂]_n (7)[Co( 2, 3-pdc )( H₂O )₂]_nⅱCd-M (M = Co,Ni) heterometallic polynuclear coordination polymers (8) and (9) (8)[CoCd₂( btc )₂( H₂O )4·2H₂O]_n (9){Na₂[NiCd₂( btc )₂( H₂O )4]( OH )₂}nⅲM (M = Fe,Co,Cd) mononuclear/polynuclear complexes (10)¹⁴ (10)[Fe( 2, 5-pdc )( H₂O )₂·H₂O]_n (11)[Fe( phen )₂( CN )₂]·CH₃CH₂OH·2H₂O (12)[Fe( phen )₂( CN )₂]·3H₂O (13)Co( C₈H₇O )₂( Imh )₂·C8H8O_·H₂O (14)[Cd( phth )( Pz )₂( H₂O )]_n (H₂suc = succinic acid, H₂phth = phthalic acid, Imh = imidazole, Pz = pyrazole, C8H8O = methylbenzoic acid, H₃btc = benzene-1,3,5-tricarboxylic acid, H₂pdc = pyridine- dicarboxylic acid, phen = 1,10-phenanthroline) All the coordination polymers are characterized by IR, UV-Vis-NIR, surface photovoltage spectrum (SPS), which are all compared and assigened. The surface electron behaviors of polymers under light-inducement were studied by SPS, which were also associated with the UV-Vis absotption spectra. The results are presented as follows:①The photo-electric properties of polymers were determined and comparatively analized. We found that there are obvious response bands in the range of 300⁸00 nm under UV-Vis light-inducement indicating the photo-electric conversion signals were generated by the light-inducement, which reveal that fourteen polymers possess photo-electric conversion properties.②There are good corresponding relationships beteen SPS and UV-Vis absorption spectra.③The micro coordination enviroment of center metal ions influence the SPS. For example, polymers (1)³ are all 3D strcutre with Co(II) as central metal and suc groups as ligand, while the mico coordination environment is different obviously. There are seven and five crystalgraphic independent Co(II) ions in (1) and (2), respectively, which are six-coordinated with distorted octahedral environment, but the mico coordination environment is different resulting in the complicated response bands aroused by d-d* transition. There are many splited and small peaks in the range of 500⁸00 nm, which broadened the response bands of the SPS. The Co(II) ions in (3) are four-coordinated with nearly tetrahedral symmetry, which make the SPS of (3) been different from the SPS of (1) and (2).④The dimensional structure of polymers influence the intensity of SPS: (4) > (6) > (13). Polymer (4) is 3D strcture bridged by suc and Im groups. The polymer (6) is 1D structure bridged by phth groups and further connented into 2D structure by hedrogen bonds, while complex (13) is 2D structure by hedrogen bonds. It is obvious that the bond energy of 3D structure all by covalent bond is stronger than that of 2D structure by covalent bond and hydrogen bonds or all by hedrogen bonds, which may provided more transitional ways for electron and holes, thus the intensity of SPS is (4) > (6) > (13).⑤The property and species of ligand influence the SPS. The SPS were broadened by the conjucated organic ligand, especially the mixed organic ligands. For example, the intruducment of Im giland make the SPS of (4) ont only intensity stronger than (3), but also the width broader than (3).⑥The response scope of SPS for the Cd-M hetero-multinuclear polymers were broadened by the introducment of second mental ions. As polymer (8) is Co-Cd hetero-multinuclear polymer, the scope of SPS for (8) is broadened than that of Co-H₃btc complex, which is by the reason of the introducemnt of Cd(II) ions resulting the adjustment of inter energy leveals. All of which can be used to design new hetero-nuclear d-d' polymers, thus the new photoelectric conversion materials with wide absotption wavelength scopes may obtained.Moreover, the relationships between synthesis and strcture of Co(II) homo-multinuclear polymer and Cd-M hetero-multinuclear polymers were discussed.