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Understanding of Intramolecular Charge Transfer Dynamics of a Push-Pull Dimethylamino-phenylethynylphenyl-dicyanoimidazole by Steady-State and Ultrafast Spectroscopic Studies
Authors: Mandal Haraprasad | Rao J. Laxmikanth | Kulhánek Jiří | Bureš Filip | Bangal Prakriti Ranjan
Year: 2023
Type of publication: článek v odborném periodiku
Name of source: Journal of Physical Chemistry C
Publisher name: American Chemical Society
Place: Washington
Page from-to: 4724-4740
Titles:
Language Name Abstract Keywords
cze Pochopení dynamiky přenosu intramolekulárního náboje v push-pull dimethylamino-fenylethynylfenyl-dikyanoimidazolu pomocí spektroskopických studií Fotofyzikální chování D-pi-A sloučeniny 2-{4-[4-(N,N-dimethylamino)fenylethynyl]fenyl-1-methyl-1H-imidazol-4,5-dikarbonitrilu (DMAP-PIDCN) bylo zkoumáno pomocí absorpce, fluorescenční emise a femtosekundové časově rozlišené absorpční a emisní spektroskopické techniky při pokojové teplotě spolu s TD-DFT kalkulací. Spektroskopické studie byly provedeny v různých rozpouštědlech s různou polaritou včetně binárních směsí rozpouštědel. Je popsána role polarity rozpouštědla, viskozity a teploty na relaxačním mechanismu DMAPPIDCN. Pozorované spektroskopické rysy byly připisovány dynamice přenosu intramolekulárního náboje (ICT). Zvýšená polarita rozpouštědla ovlivnila především fluorescenční emisní spektra ukazující na významný nárůst dipólového momentu excitovaného stavu. Tento výsledek jasně odhaluje účinný přenos náboje z donoru (N,N-dimethylamino)fenylu (DMAP) na akceptor fenyl-1-methyl-1H-imidazol-dikarbonitril (PIDCN) v excitovaném stavu v polárním prostředí. přenos elektronů; excitovaný stav; duální fluorescence; vodíková vazba; chromofory; absorpce; barviva; relaxace; emise
eng Understanding of Intramolecular Charge Transfer Dynamics of a Push-Pull Dimethylamino-phenylethynylphenyl-dicyanoimidazole by Steady-State and Ultrafast Spectroscopic Studies Photophysical behaviors of D-pi-A compound 2-{4-[4-(N,N-dimethylamino)phenylethynyl]phenyl-1-methyl-1H-imidazole-4,5-dicarbonitrile (DMAP-PIDCN) were explored using steady-state absorption, fluorescence emission, and femtosecond time-resolved absorption and emission spectroscopic techniques at room temperature along with computational time-dependent density functional theory (TD-DFT) calculation. The spectroscopic studies were carried out in different solvents of varying polarities including binary solvent mixtures. The role of the solvent polarity, viscosity, and temperature on the relaxation mechanism of DMAPPIDCN is disclosed. The observed steady-state and time-resolved spectroscopic features were attributed to intramolecular charge transfer (ICT) dynamics. The ICT in DMAPPIDCN is rationalized to a sequential twisted motion of both N(CH3)2 and whole N,N-dimethylaminophenyl moieties around the molecular axis interconnecting the adjacent imidazolephenyl moiety leading to the TICT1 and TICT2 (sigma*) states. The increased solvent polarity affected mostly the fluorescence emission spectra pointing to a significant increase in the excited state dipole moment. This result clearly reveals formation of the TICT2 (sigma*) involving efficient charge transfer from the (N,N-dimethylamino)phenyl (DMAP) donor to the phenyl-1-methyl-1H-imidazole-dicarbonitrile (PIDCN) acceptor in the excited state in a polar environment. In the TICT2 (sigma*) state, the planes of electron-withdrawing and electron-donating moieties are perpendicular with the angle (DMAP)C-CtriplebondC being 141.1°. This nonplanar arrangement accounts for the observed large Stokes shift. Time-resolved fluorescence spectroscopic studies unveil the excited state relaxation processes confirming the increase in the nonradiative decay rate in aprotic medium with increase in the solvent dielectric constants. Femtosecond transient spectroscopic studies unambiguously confirmed the existence of well separated LE and TICT fluorescence up-conversion; electron-transfer; excited-state; dual fluorescence; hydrogen-bond; chromophores; absorption; dyes; relaxation; emission

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