Synthesis and photophysics of 4′-R-2,2′;6′,2″-terpyridyl (R = Cl, CN, N(CH3)2) platinum(II) phenylacetylide complexes

Abstract

Listen

Translate article

Platinum terpyridyl (tpy) phenylacetylide complexes with -Cl, -CN, and -NMe(2) substituents on the 4'-position of the tpy ligand were synthesized and characterized. Their photophysical properties were systematically investigated. In addition, theoretical electronic structure calculations using density functional theory (DFT) and time-dependent (TD-DFT) approaches were carried out for complexes and ; the results of these calculations provided additional information on the nature of the electronic structures of the low-lying electronic states of these complexes, including the electron density distribution and the composition of the frontier molecular orbitals. Complexes exhibit moderately intense charge-transfer bands in the visible region, which are assigned to the (1)MLCT/(1)LLCT transitions. In comparison to their corresponding chloride complexes , these charge-transfer bands become broadened and red-shifted. Complexes emit at room temperature in CH(3)CN and CH(2)Cl(2) solutions and at 77 K in butyronitrile glassy solutions. At room temperature, the emission is tentatively attributed to (3)MLCT for and , and to a mixture of (3)MLCT/(3)ILCT/(3)pi,pi* for . Due to the admixture of (3)ILCT/(3)pi,pi* characters in its emitting state, displays a much higher emission quantum yield and longer emission lifetime compared to and . Replacing the chloride co-ligand in by phenylacetylide co-ligand clearly enhances the emission and prolongs the lifetime. exhibit a broad and moderately intense triplet excited-state absorption in the visible to the NIR region, with large excited-state absorption coefficients and moderately high triplet excited state quantum yields. Therefore, complexes , especially , have potential applications in organic light emitting devices (OLED) and as reverse saturable absorbing materials.