Synthesis, structure, and surface photovoltage properties of a series of novel d7-d10 metal complexes with pincer N-heterocycle ligands

Novel d(7)-d(10) complexes Cu(bpz(star)eaT)(SCN)(2) (1), Ni(bpz(star)eaT)(SCN)(2) (2), Co(bpz(star)eaT)((SCN)(2) (3), [Ni(bpz(star)eaT)(N-3)]center dot H2O (4) and Co(bpz(star)eaT)(N-3) (5) (bpz(star)eaT: 2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-diethylamino-1,3,5-triazine) were synthesized by the reaction of a metal salt (CuCl2 center dot 2H(2)O, NiCl2 center dot 6H(2)O, CoCl2 center dot 6H(2)O or Co(CH3COO)(2)center dot 4H(2)O), pincer N-heterocyclic ligands and KSCN or NaN3 in either acetonitrile or a mixed solution at different temperatures. The structures of these complexes were characterized by elemental analysis, IR and UV-Vis spectroscopy, powder X-ray diffraction (PXRD), thermogravimetric analyses (TG) and single-crystal diffraction analysis. Structural analysis reveals that the metal atoms (Cu and Co) in complexes 1, 3 and 5 are in a five-coordination mode, forming distorted square pyramid geometries with N5 donors; Ni atoms in the complexes 2 and 4 are in a six-coordination mode, forming slightly distorted octahedra with the set of N5S and N6 cores, respectively. In complexes 1-5, the auxiliary N-donor monodentate ligands were only connected with one metal center. In complexes 2 and 4, the two metal centers were connected by bridging coordinated SCN- and N-3(-), which were different from those in complexes 1, 3 and 5. In addition, surface photovoltage properties of the five complexes have also been studied and discussed in detail. Surface photovoltage spectra (SPS) of the complexes 1-5 show that the surface photovoltage (SPV) response signals increase when the positive electric field is enhanced in the range of 300-800 nm. The results show that these complexes possess potential p-type semiconductor properties and their uses may be extended to semiconductor materials.