| Near-infrared（NIR）luminescence materials have broad application prospects and commercial value in the fields of energy military,information security,biomedicine,and optical fiber communication due to their excellent properties.Square-planar Pt（II）complexes have abundant excited state energy levels and are prone to form different aggregated states in the molecular axial direction via Pt-Pt interaction orπ-πstacking interaction between the aromatic rings of the luminescence ligands.The effective reduction of luminescence energy makes Pt（II）complexes become a new hotspot in the study of NIR luminescence materials.However,restricted by the energy gap law,NIR luminescence Pt（II）complexes with wavelengths over 1000 nm are still rare,which severely limits the wider application of such materials.Here,twenty-two kinds of square-planar coordinated Pt（II）-alkyne complexes were synthesized using substituted 2,2’-bipyridine as ligand.By combining the one-dimensional（1D）Pt wire stacking structure with the electronic effect of substituent and enhancing the Pt-Pt interaction strategies,the NIR luminescence of complexes over 1000 nm were successfully achieved.In addition,the transformation from visible light to NIR light is also attempted by using external stimulus signals.Finally,by systematically studying the relationship between structures and NIR luminescence properties of complexes,effective strategies for constructing NIR luminescence Pt（II）complexes were explored.Specific research contents are as follows:（1）Ten kinds of planar Pt（II）-alkyne complexes Pt（Di Clbpy）（C≡C-C6H4-R-4）2[R=Me（1）,R=Et（2）,R=i-Pr（3）,R=t-Bu（4）,R=C≡Ct-Bu（5）]and Pt（Di Brbpy）（C≡C-C6H4-R-4）2[R=Me（6）,R=Et（7）,R=i-Pr（8）,R=t-Bu（9）,R=C≡Ct-Bu（10）]were synthesized using4,4’-dichloro-2,2’-bipyridine and 4,4’-dibromo-2,2’-bipyridine as ligands,respectively.These ten complexes all have 1D Pt wire stacking structures,and the NIR luminescence of these complexes above 900 nm were successfully realized by combining the electronic effect of ligand substituents.Among them,the maximum emission wavelength of 2·?（THF）reaches1044 nm.Through the systematic study of crystal structures and luminescence properties,the basic rules for constructing 1D Pt wire stacking structure were explored,and confirmed that the combination of 1D Pt wire stacking structure and electronic effect of substituent is one of the effective strategies for designing NIR luminescence Pt（II）complexes with longer emission wavelength.（2）To achieve stable NIR luminescence of Pt（II）complexes,six kinds of planar Pt（II）-alkyne complexes Pt（Di TESbpy）（C≡C-C6H4-R-4）2[R=Me（11）,R=Et（12）,R=t-Bu（13）,R=F（14）,R=Cl（15）,R=Br（16）]based on 4,4’-bis（triethylsilylethynyl）-2,2’-bipyridine ligand were synthesized.By constructing Pt（II）dimers with ultra-short Pt···Pt distance,the NIR luminescence of these complexes were successfully achieved by enhanced Pt-Pt interaction.Among them,the emission peak position of complex 12 is at 1062 nm,which is the longest emission wavelength of Pt（II）complexes based on 2,2’-bipyridine ligands reported so far.In addition,these complexes also showed good stability under external stimuli due to their dimer structures with enhanced Pt-Pt interactions.This discovery provides a new idea for designing simple and stable NIR luminescence materials.（3）Six kinds of planar Pt（II）-alkyne complexes Pt（Di TMSbpy）（C≡C-C6H4-R-4）2[R=Me（17）,R=Et（18）,R=t-Bu（19）,R=F（20）,R=Cl（21）,R=Br（22）]based on 4,4’-bis-（trimethylsilylethynyl）-2,2’-bipyridine ligand were synthesized.The NIR luminescence of six complexes were induced by external stimuli.By this method,some complexes with visible luminescence under conventional conditions can achieve NIR luminescence.In addition,these complexes also have good application prospects for the identification of specific organic vapors.The related researches provide certain theoretical bases and experimental materials for the molecular design of NIR luminescence materials based on Pt（II）complexes. |
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