Synthesis,Structure And Photophysical Property Of Homo-/Hetero-metallic Coordination Polymers Constructing From Rich Nitrogen Heterocyclic And Flexible Multi-carboxylate Ligands

Five coordination polymers containing L-type?L¹,L²,L³?ligands have been designed and synthesized by the hydrothermal methods with Co????Cu???and Ni???ion as central metal and cis/trans-maleic acid and N-heterocyclic ligands as precursor ligands.Five polymers and two kinds of supramolecules have been synthesized by the bridging ligands of aromatic carboxylates together with N-heterocyclic ligands as co-ligands.The structures were obtained and determined by X-ray single crystal diffraction.The formulas are listed as follows:?1?[Cu₂?L¹?₂?H20?₄]_n?7?[Cu₂Cd?2-ip?₂?H20?₂]_n?2?[CuCd?L¹?₂?H20?₄]_n?8?[Co?1,3-bdc??amp?]_n?3?{[Ni?L²??H20?₂]?H20?} n?9?[Co?1,3-bdc??dmpz?₂]_n?4?[Co?L²??H20?],?10?[Cu?1,3-bdc??Pz?₂]_n?5?[Co?HL³?₂]?11?[Cu?phen??H20?₂]·SO₄?6?{[Cu₂?1,2-bdc?₂?bipy?₂?H₂O?]·3H₂O}n?12?Cu?2-Picid??H₂O?₂?H2L¹=2-?1-pyrazol?-succinic acid?,H2L²=2-?3,5-dimethylpyrazol?-succinic acid,HL³=2-?piperazine?-succinic-acid,1,2-bdc=1,2-phthalic acid,2-ip=2-hydroxyisophthalic acid bipy=2,2-bipyridine,1,3-bdc=1,3-phthalic acid,amp=2-aminopyrimidine,dmpz=3,5-dimethylpyrazole,pz=pyrazole,phen=1,10-phenanthroline 2-picic=picolinic acid)Crystal structure analysis shows that coordination polymers?1?-?5?are in-situ self-assembly synthesized by new type of hgand?L?.?1???4?are 2D coordination polymers and?5?is bridged to 3D supramolecule by hydrogen bonds.The Polymers of?6?-?10?are bridging by the ligands of 1,3-bdc/1,2-bdc together with N-heterocyclic as co-ligands.?1 1?-?12?are coordination supramolecules linked by weak intermolecular interactions.All of the polymers are characterized by IR,UV-Vis absorption spectra,SPS and FISPS spectra.Compared and analyzed the surface electron behavior under the inducement of UV-Vis light on the basis of structural data,the following conclusions are found:?1?The photovoltage responses of?1?-?12?are gradually increasing with the external electric fields,which indicates that these polymers possess the characteristic of p-type semiconductor.?2?The change of photovoltage responses at ?max=352nm of?1???12?is different with the increase of the applied electric field.?The introduction Cd²⁺with larger dispersion degree of 4d orbital will affect the increscent extent of the photovoltage response intensity.For example,when applied external electric fields are from OV to 6V,the photovoltage response intensity of?1?and?2?are similar.While the external field is above 6V,the FISPS of?2?was strikingly enhanced,?2?>?1?.It indicates that the introduction of Cd²⁺in polymer?2?may provide more transitional ways for electrons and holes due to the larger dispersion degree of 4d orbital in space,which leads to the non-equilibrium carriers in?2?more effectively migration.This phenomenon is observed in polymers?6?,?7?and?10?.?The structural dimension of polymers affect the intensity of SPS and FISPS.For example,when applied external fields from 0OV to 4V,the photovoltage response intensity of?8?and?9?are similar.While the external field is above 4V,the photovoltaic response intensity of?8?is strikingly enhanced.It indicates that the 3D H-bonding network in polymer?8?may provide more transitional ways for electrons and holes than 1D structure of?9?.In addition,the coordination supramolecules of?11?and?12?are observed the similar phenomenon.?3?The conjugation degree of ligand will affect the width of SPS response band.When comparing the SPS of polymers?3?,?4?and?5?,we found that the width of response bands?3?^?4?>?5?.This may be due to that?3?and?4?containing the ligand of pz ring,which make the conjugate stronger than the ligand of ppz in?5?.The extent of conjugation degree is larger,the separation of carrier is easier.Under the external electric fields,the photovoltage response was red-shifted to the visible region,namely,broadening the width of response bands.