Syntheses, Structures, and Steady State and Time Resolved Photophysical Properties of a Tetraiminodiphenol Macrocyclic Ligand and Its Dinuclear Zinc(II)/Cadmium(II) Complexes with Coordinating and Noncoordinating Anions

摘要

The work in the present investigation reportsnthe syntheses, structures, steady state, and time-resolvednphotophysical properties of a tetraiminodiphenol macrocyclicnligand H2L and its eight dinuclear zinc(II) complexes and onencadmium(II) complex having composition [Zn2L(H2O)2]-n(ClO4)2·2CH3CN (1), [Zn2L(H2O)2](ClO4)2·2dmf (2),n[Zn2L(H2O)2](NO3)2·2dmf (3), [Zn2LCl2] (4), [Zn2L(N3)2]n(5), [Zn2L(NCS)2] (6), [Zn2L(NCO)2] (7), [Zn2L-n(NCSe)2]2·dmf (8), and [Cd2L(OAc)2] (9) with variousncoordinating and noncoordinating anions. The structures of allnthe complexes 1−9 have been determined by single-crystal X-ray diffraction. The noncovalent interactions in the complexesnresult in the generation of the following topologies: two-dimensional network in 1, 2, 4, 6, 7, 8, and 9; three-dimensional networknin 5. Spectrophotometric and spectrofluorometric titrations of the diprotonated salt [H4L](ClO4)2 with triethylamine as well asnwith zinc(II) acetate and cadmium(II) acetate have been carried out, revealing fluorescence enhancement of the macrocyclicnsystem by the base and the metal ions. Steady state fluorescence properties of [H4L](ClO4)2 and 1−9 have been studied andntheir quantum yields have been determined. Time resolved fluorescence behavior of [H4L](ClO4)2 and the dizinc(II) andndicadmium(II) complexes 1−9 have also been studied, and their lifetimes and radiative and nonradiative rate constants have beenndetermined. The induced fluorescence enhancement of the macrocycle by zinc(II) and cadmium(II) is in line with the greaternrate of increase of the radiative rate constants in comparison to the smaller rate of increase of nonradiative rate constants for thenmetal complexes. The fluorescence decay profiles of all the systems, being investigated here, that is, [H4L](ClO4)2 and 1−9,nfollow triexponential patterns, revealing that at least three conformers/components are responsible to exhibit the fluorescencendecay behavior. The systems and studies in this report have been compared with those in the reports of the previously publishednsimilar systems, revealing some interesting aspects.