Design, Synthesis And Tenebrescence Luminescence Properties Study Of N-heterocyclic Complex

Tenebrescence luminescence materials have attracted extensive interest for their promising applications in sensors,deformation detectors,security systems,luminescence switch and memory devices.In order to solve the problems of poor thermal stability and difficult synthesis of organic chameleon luminescence materials,so in recent years the chameleon luminescence system of the metal-organic complexes has attracted wide attention.According to molecular engineering and design,the rigid planar molecules with extended conjugated ? electrons are advantageous for the synthesis of luminescent materials.In addition nitrogen-containing heterocycles that are well known as lightsensitive components and electron-deficient heterocyclic rings that have been proven to be well suited to give rise to strong ?-? interactions.Herein two terpyridyl derivative molecules,4'-?4-pyridyl?2,2':6',2"-terpyridine?PYTPY?and 4'-?4-carboxyphenyl?-2,2':6',2"-terpyridine?CPTPY?,are selected as the ligand to build five stimuli-responsive metal-ligand complexes.The specific research results obtained are as follows:1.Two mononuclear nitrogen heterocyclic complexes,compound 1[Zn?PYTPY?]Cl₂ and compound 2[Zn?CPTPY?]Cl₂·2H₂O,were synthesized by self-assembly of zinc chloride and PYTPY or CPTPY.Due to the different stacking pattern between compound 1 and 2,only compound 1 exhibits interesting mechanochromic luminescence behavior.Structure analysis and PXRD data show that the crystal lattice was destroyed and the phase convert from the crystalline to the amorphous phase during the grinding process,and the weak ?-? interactions?3.9072?12?A?and C-H...? interactions in compound 1 were changed by grinding.So the yellow-green emission of compound 1 was converted into blue-purple emission after grinding.In addition,under light irradiation,compound land 2 form photo-generated free radicals and accompany with the change of luminescence.There is complete overlap between the UV-Vis absorption spectra of compound 1 after light irradiation and the PL spectra spectra of compound 1,which causes the energy resonance transfer leads to luminescence quenching.But the UV-Vis absorption spectra and fluorescence spectra overlap partially for compound 2,which causes partial resonance energy transfer leads to luminescence changing.2.A binuclear N-heterocyclic complex with reversible mechanochromic luminescence behavior,compound 3[Zn₂?PYTPY?₂?O₂C-C₆H₄-CO₂?]Cl₂,was synthesized by self-assembly of ZnCl₂,PYTPY and 1,4-dicarboxybenzene.Compound 3 gives orange emission,and it is converted into blue-purple emission after grinding.According to the PXRD data,the crystal phase of compound 3 converts from the crystalline to the amorphous phase after grinding and the amorphous phase is repaired after water vapor treatment accompany with blue-purple emission converted into orange emission.So the reversible mechanochromic luminescence behavior causes by transformation of crystal phase.3.Two nitrogen heterocyclic coordination supermolecules,compound 4[Zn?PYTPY??BDC?]·3H₂0 and compound 5[Zn?CPTPY??BDC?]·2H₂0,were synthesized by PYTPY?for 4?,CPTPY?for 5?,1,3-dicarboxybenzene?H₂BDC?and ZnCl₂ using hydrothermal method.Although compound 4 and 5 have similar coordination modes and one-dimensional chains,only 4 exhibits interesting mechanochromic and thermochromic luminescence behaviors due to different stacking modes between 4 and 5.According to the structural analysis and the PXRD data,the two-dimensional layers of 4 were formed from a face-to-face ?-?interaction between the PYTPYs of the neighbouring chains and three dimensional structure is formed by interlayer forming multiple hydrogen bonds with solvent water molecules.Such multiple hydrogen bonds is easy changed by grinding and heating and is restored to the initial state after the sample is treated with water vapor,which causes mechanochromic and thermochromic luminescence behaviors.