Squaraine Dye Structure And Photoconductivity Study

AbstractphotoconduCtivity The geometries of b is [4 - (d Anethy1 amino)p henyl] s qu araineand its eight dervations have been ophmized by RHF6-31G**, W/3-21G'*,B3W/6-3lG**, AMl and PM3, and the geometries of eight unsymmetrical squarainedyes by ns6-31G**. The relationships betWeen the populations of charge of themand their dark 4ecay values and their photosensitivity have been studied. The resultssuggest that their intramolecular charge-transfer charactee charges of O in their C4O:and sizes of- their substituents be importat factors Which affect thedphOtoconductivity As the Va1ues of these factors are small, their photosensitivity Wil1loW but their dark decay va1ues increase.Electronic SpeCtfa The geometries of excited singlet, triPlet and ground statesand redox forms of twO squaraine dyes, b is [4 - (dimethyl amino)p henyl1 s qu araine andb is [4 - (dim ethy1 amino) - 2 -hydroxyp henyl1 s qu araine, have b e en op timiz e d b yNpe)/3-21G'*and CIS/3-21G**. The resu1ts indicate that the changes ofgeometries and populations of charge oftrinlet states are the most obvious, and thecalculated wavelengths of electronic speCtra are in rational agreemellt With theavailable exPermental values. The geometres of excited singlet, ground states andredox fOrms of b is [2' 4, 6 -trihy droxyP heny11 s qu araine d y e hav e b e en optimized byW3-2lG"and CIS/3-2lG**. And their electronic spectra have been calculated byCIS/3-2lG', ZINDO and CIS/6-3lG', Which are not in agreement wth the.' exPerimeotal values in the reference. Then the linear relationships between theexPerimenta1 values with calculated ones and MO's energies have been studied, andthe results show the exPerimelltal largest wave1engths of their absorPtion spectra arelikely to be generated by sq, sq-, sqa-and sqs-, but not by sq+, sq, sq- and sq:-.' Thermodynamic Properties The geometries and thermodynamic properties offOur b is [4- di alkyl amino -2 - hy droxyP henyl1 s qu araine dy e s and one b is [ind o 1um]squaraine dye have been calcaluted by RHF3-21Q and the results show the coexistsof their cis and trans isorpers are thermodynamica11y permitted, and the ratios of themhave been calculated. The probabIy stab1e geometries of tow squaraine dyes,b is [2, 4, 6-trihydroxyhenyl] squ araine dye and bi s [2, 4- dinydroxy heny l ] squ arainedye and their dhaers, have been oPtindzed by AMl, and then the most stablegeometries of them by m-21G" and thermodyntalc values have been eshmated.The results show their dAnerizations are exothedc.Key Words Spuaraine Dyes, Photoconductivity,Electronic Spectra, Thermodynamic Properties, Ab initio.