| Recently, startling interest for metal complexes with the unusual photophysical properties, is stimulated by the continuously expanding need for luminescent materials. In this respect, Schiff base ligands have proven to be excellent directional ligands, in particular in those cases where additional various diimine have been introduced in the backbone of the ligand scaffold. Such systems are best designated as cleating because the usual central N4coordination pocket, forming a N4cavity into which a wide variety of cations can be assembled. Selective introduction of metal ions in the N4pockets can be achieved to furnish p-block, d-block, f-block metallic complexes that can be of great use in luminescent materials.In this dissertation, eight ligands can be obtained from a typical condensation reaction (diamine with2-pyridine-carboxaldehyde and their derivatives). These symmetrical and assymmetrical multidentate ligands have a rigid, semi-rigid or fully flexible backbone, which can offer several positions for coordination and hydrogen bonding interactions，and their photophysical properties could be further enhanced on coordination. The complexes are characterized by means of UV-vis,1H NMR,13C NMR, IR spectroscopy and elemental analysis. The structures of three ligands and twenty-seven complexes are determined by X-ray single-crystal analysis. A systematic work is developed to discuss on the effect of polarity of solvent, deuterated reagent and temperature on luminescent properties.A systematic study of twelve divalent transition metal (ZnII, HgII) complexes with a series of N4-or novel N4O2-donor Schiff base ligands formulated as [M(L1)Cl2](L1=N,N′-bis(2-pyridinylethylidene)phenylene-1,2-diamine, M=Zn, Zn1; M=Hg, Hg1),[M(L2)Cl2](L2=N,N′-bis(2-pyridinylethylidene)toluene-3,4-diamine, M=Zn, Zn2; M=Hg, Hg2),[M2(L3)Cl4]·nCH2Cl2(L3=N,N′-bis(2-pyridinylmethylene)cyclohexane-1,2-diamine, M=Zn, n=0, Zn3; M=Hg, n=1, Hg3),[M2(L4)Cl4]·nCH3OH (L4=N,N′-bis(2-pyridinylethylidene)cyclohexane-1,2-diamine, M=Zn, n=1, Zn4; M=Hg, n=0, Hg4),[M2(L5)Cl4](L5=N,N′-bis(3-methoxy-2-pyridinylmethylene)-cyclohexane-1,2-diamine, M=Zn, Zn5; M=Hg, Hg5),[M2(L6)Cl4]·nCH3CN (L6=N,N′-bis(3-methoxy-2-pyridinylmethylene)butane-1,4-diamine, M=Zn, n=4, Zn6; M=Hg, n=0, Hg6) have been conducted by reactions of the corresponding rigid (L1, L2), semi-rigid (L3, L4and L5) and flexible (L6) Schiff base ligands with ZnCl2or HgCl2, respectively. Depending upon the nature of the spacer in between two iminic bonds, the series of molecules display bright luminescence with emission maxima ranging from blue to red. Such surprising variation is ascribed to the transition from π*to π of ligand. The lifetimes of all the molecules are microsecond scale. The quantum yields have been determined to be in the range of0.013–0.143for ZnII complexes and0.043–0.131for HgII complexes. Time-dependent density functional method (TD-DFT) calculation results demonstrate that the absorption of ligand L5and corresponding complexes (Zn5, Hg5) is in line with the experiments.A series of lanthanide complexes [LnL3(NO3)3]·CH3CN [Ln=Ce,(Ce1); Nd,(Nd2); Tb,(Tb3); Dy,(Dy4); Ho,(Ho5); Er,(Er6); Tm,(Tm7); Yb (Yb8)] has been synthesized by the reaction of N4chelate ligand (L3) with lanthanide salts. Photoluminescence spectra of complexes Nd2, Tb3, Dy4, and Yb8show the strong characteristic luminescence from visible to near infrared (NIR) region. Further, the singlet state (32467cm–1) and the lowest triplet (23202cm–1) energy level of L3are calculated, indicating that the energy transfer from L3to Tb3+ion is more effective than that to Dy3+ion. An extended work is developed to discuss on the effect of deuterated reagent and temperature on luminescent properties of Tb3and Yb8.A indium complex {[InL3(NO3)(OH)]·NO3·CH3OH}2(In1) is isolated from the refluxing reaction of ligand (L3) and an In(III) nitrate hydrate in mixed solvent. Center metal In3+ion is seven-coordinated, giving rise to a [N4O3] kernel and a distorted monocapped trigonal prismatic geometries. Complex In1exhibits a pronounced bathochromic shift in emission spectra as solvent polarity increases (polarity order: DMSO> CH3CN> CHCl3), indicating a change in dipole moment of1upon excitation. Further bathochromic shift exists in CH3OH (467nm) solution, which is attributable to the hydrogen bond donor ability of CH3OH as polar protic solvent. The lifetimes of In1and L3belong to the millisecond scale and In1is longer than L3under solid state. Moreover, the lifetimes of In1and L3in the solid state are shorter than that in solution. An extended work is developed to discuss on maximum emission and lunminescent lifetime dispersed in the deuterated reagents. Commission Internationale de L’Eclairage (CIE)1931demonstrates that the color gamut of In1and L3is blue.Benzimidazole derivatives L7and L8are synthesized by the reaction of1,2-diaminobenzene and6-methoxy-2-pyridinecarboxaldehyde. Five IIB group complexes that contain L7and L8have been synthesized. Their formulas are [ZnL7Cl2](Zn7),{[CdL7Cl2]}2(Cd7),[Cd(L7)2(NO3)2] H2O (Cd7′),[HgL7Cl2](Hg7), and [ZnL8Cl2](Zn8), respectively. The structures of these complexes testify that the ionic radius and counterions (Cl–and NO3–) cooperatively affect the coordination mode of center metal. As the small and medium radius, four-coordinated Zn2+(Zn7and Zn8) and five-coordinated Cd2+(Cd7) possess tetrahedron and trigonal bipyramid geometries. Though Hg2+(Hg7) has larger radius, the three-coordinated geometry shows trigonal planar in order to eliminate the repulsive force. Further observations illustrate that Cd2+(Cd7′) is binded two ligands L7when NO3–as counter anions, forming seven-coordinated monocapped trigonal prismatic geometries. These complexes display bright blue luminescence with the emission maxima (λmax) ranging from399to499nm at ambient temperature, depending on the N,N′-chelating ligand-centered π*→π transition. Upon cooling to77K, complexes show rich structured emission profiles compared to that at room temperature. The lifetimes of ligands and complexes belong to microsecond scale. The emission efficiency of complexes is found with quantum yields ranging from0.23to0.40.Three lanthanide coordination polymers have been successfully synthesized under hydrothermal or solvothermal conditions, namely [Ln(2,4′-bpdc)(1,4-bdc)0.5(DMF)·(H2O)·H2O]n [Ln=Pr (Pr1); Ln=Nd (Nd1)],[Ln(2,4′-bpdc)(DMF)2NO3]n [Ln=Nd (Nd3)](2,4′-H2bpdc=2,4′-biphenyldicarboxylic acid,1,4-H2bdc=1,4-benzenedicarboxylic acid). X-ray crystallographic studies reveal that Pr1and Nd1are isostructural and exhibit2D (3,4)-connected net structures. Nd3show2D layered structures containing double helix chains (Δ and Λ) with44topology. Furthermore, Complexes Nd1and Nd3display characteristic luminescent properties for Nd(III) in near-infrared region. |
PDF Full Text Request