Platinum(II) coordination compound with 4′-[4-(dimethylamino)phenyl]-2,2′:6′,2″-terpyridine – The new insight into the luminescence behavior and substituent effect

Abstract

{PtCl[4′-(4-NMe2)-Ph-terpy-κ3N]}BPh4·CH3CN (1) was synthesized and its structural, electrochemical and photophysical properties were characterized in comparison to previously described systems of [PtCl(4′-Ph-terpy-κ3N)]+ and [PtCl(4′-NMe2-terpy-κ3N)]+ to determine again the significance of the appropriate design of substituent in case of luminescence behavior of transition metal complex. The molecular formula of compound was confirmed by.X-ray analysis, elemental analysis, FT-IR and NMR studies. The geometries of ground and excited states of compound were also calculated on the basis of Density Functional Theory (DFT) method. The electrochemical properties were elucidated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The electronic absorption spectra of compound (1) in solutions are similar to those in described previously platinum(II) terpyridine coordination compounds. The photoluminescence properties were studied in various media to rationalize effects on emission properties caused by substituent, solvent polarity, concentration of solution and rigidity of media. The studied compound displays enhancement of photoluminescence properties in comparison to [PtCl(terpy-κ3N)]+ system, however its emission lifetime in the regard to [PtCl(4′-Ph-terpy-κ3N)]+ and [PtCl(4′-NMe2-terpy-κ3N)]+ is significantly decreased. This suggest the impeded charge transfer from electron-rich NMe2 group via phenylene bridge to the terpy core due to the unfavorable, inclined geometry of excited state. As a consequence of substituent twisting on the path S0 → S1 → T1, the interference of 3ILCT and 3MLCT excited state is disturbed favouring the non-radiative deactivation process of {PtCl[4′-(4-NMe2)-Ph-terpy-κ3N]}BPh4·CH3CN.