Syntheses And Optical Properties Of Nitrogen Aromatic Heterocyclic Supramolecules

Metal complexes,which contain organic ligand and metal ion,have attracted much attention in many fields due to the flexible combination of organic ligand and metal ion.Many efforts have been devoted to design the complexes,which exhibit preconceived structures and properties by choosing the appropriate ligands and metal ions.In this work,five ligands?2-methoxyphenyl?-pyridine-methyleneamine?L1?,?2-methoxyphenyl?-pyridine-2-methylmethyleneamine?L2?,?2,4,6-trimethylphe nyl?-pyridine-2-methyleneamine?L3?,?2,6-diethylphenyl?-pyridine-2-methy-leneami-ne?L4?,?2,6-diisopropylphenyl?-pyridine-2-methyleneamine?L5?were obtained from the typical condensation reaction with 2-pyridine-carboxaldehyde,2-acetylpyridine,o-methoxyaniline,2,4,6-trimethylbenzenamine,2,6-diethylaminobenzen and 2,6-diisopropylaniline.These five ligands,together with 1,3-bits?2-benzimida-zolyl?benzene?BIB?and 3-quinoline carboxylicacid?3-Hqldc?,reacted with different metal salts under a hydrothermal/solvothermal method.Seven complexes Hg?L1?Cl₂?1?,Zn?L2?Cl₂?2?,Cd?L3?₂?NO₃?₂?3?,Cd?L4?Cl₂?4?,Cd?L5?Cl₂?5?,{[Zn?BIB??OAc?]?H₂O}_n?6?and [Zn?3-qldc?₂]n?7?were obtained.These complexes were characterised by single-crystal X-ray analysis,IR spectrum,1H NMR,and UV-vis absorption.Then the luminescent properties were discussed.After this,N,N'-bis?2-pyridineimine?o-phenylenediamine?BPPI?was employed as cosensitizers in combination with N719 in dye sensitized solar cells?DSSCs?to study its co-sensitization performance.X-ray crystalographic analysis reveals that complex1 was the orthorhombic crystal system,and 2⁵ crystallizes was the monoclinic system.Dimer units of 1 were linked to each other by ?-? stacking interaction and given rise to the formation of infinite one-dimensional?1D?chain.The C–H···Cl hydrogen bonds connected two adjacent molecules of complex 2,presenting one-dimensional infinite pore structure along the b direction.Facilitated by the C–H···Cl hydrogen bonding.these chains are linked with each other into a two-dimensional?2D?lamellar structure.In crystal,molecules are further packed into a three-dimensional?3D?supramolecular network via intermolecular interactions.For complex 3 and 5,the widespread presence of hydrogen bonding interactions extend the array into the 2D?4,4?-connected sql topological net work;The comections of the dimer units via C–H···Cl hydrogen bonds lead to the formation of 1D ladder chain of complex 4.The complex 6 and 7 crystallized in the triclinic system,belonged to Pnna and C2/c space group,respectively.Complex 6 exhibits 1D zigzag chain structure,with ?–? stacking and hydrogen bond interactions linking modularunits into a 3D supramolecular architecture;while complex 7 exhibits 2D?4,4?-connected sql net work,which further forms 3D distorted cpu topological structure with ??? stacking interaction.Fluorescence spectra shown that complexes 1⁵ emited a light-emitting region from blue,green to yellow,which scattered in the middle part of the chromaticity diagram.Complex 1 generated emitting color close to white.It has been demonstrated that the light color of the complex can be controlled by changing the electronic group and centeral metal ion.The fluorescence emission of complex 1⁵ mainly contributed to the ?*?? transition of organic ligands in the pyridine ring.Namely,the contribution of benzene ring and central metal ions was small.Solid state luminescent tests revealed that complex 6 displayed blue fluorescence with maximum emission peak of 430 nm.The maximum emission peak of 6 was 27 nm,red shift compared with that of free ligand BIB.It was because the difference between the ground state and the excited state energy was decreased by the coordinate bond interactions of zinc and ligand.The complex 6 exhibited strong blue emissions,with emission peaks of 404 nm.The fluorescence emission spectrum of 6 in DMSO solution was narrower than that in solid state.This was because the hydrogen bonds and ?–? stacking interactions among molecules in the solid state.The maximum emission of complex 7 was 444 nm,which was similar with that of ligand 3-Hqldc.It was shown that the solid fluorescence of complex 7 was mainly based on the ?*?? transition of ligand with metal perturbation.We further examined the fluorescent properties of complex 7 in DMSO,CH3 CN,and Me OH solvents.The different polarities of solvents did not alter the maximum emission.The lifetimes of complex 7 in solid state increased conspicuously to those in solutions,because of the less polar nature of the environment in solid state.There was better coplanarity in the solid state,which was conducive to the generation of fluorescence.As BPPI?8?can compensate the absent absorption of ruthenium complex N719 in the low wavelength region of the UV-visible spectrum,the BPPI was used as co-sensitizer in combination with N719,to investigate its effect on enhancing the performance of dye-sensitized solar cells?DSSCs?.The results demonstrated that co-sensitization could enhance spectrum responded by Ti O2 photoelectrodesin DSSCs,inhibiting the surface recombination of electrons at the electrode/electrolyte interface and extending the life of the electronic,reducing the total resistance of DSSCs.The overall conversion efficiency of DSSCs,which was co-sensitized with BPPI was higher by 17.58% than that without BPPI.