A combined spectroscopic and computational investigation on the solvent-to-chromophore excited-state proton transfer in the 2,2′-pyridylbenzimidazole–methanol complex

Abstract

This article demonstrated experimental proof of excited state ‘solvent-to-chromophore’ proton transfer (ESPT) in the isolated gas phase PBI (2,2'-pyridylbenzimidazole)-CH3OH complex, aided by computational calculation. The binary complexes of PBI with...

Spectroscopic Characterization of Hydrogen-Bonded 2,7-Diazaindole Water Complex Isolated in the Gas Phase

“…A similar observation of the large red shift of the band origin of water and methanol complexes of 2,2′pyridylbenzimidazole was also reported recently. 34,35 The red shift also implies that H 2 O is hydrogen bonded to the N(1)-H a and N(7) sites of the chromophore. This is similar to that of the 7-azaindole-H 2 O (7AI-H 2 O) complex, where the band origin at 33,354 cm −1 was red-shifted by 1285 cm −1 compared to the bare 7AI (0 0 0 at 34,639 cm −1 ).…”

Competing Excited‐State Hydrogen and Proton‐Transfer Processes in 6‐Azaindole‐S3,4 and 2,6‐Diazaindole‐S3,4 Clusters (S=H2O, NH3)

“…The chromophores display higher photo‐acidic character and considered as the main reason for the photophysical and photochemical processes. Recently, experimental investigations aided by computational calculations proposed a novel deactivation mechanism in the excited biomimetic molecule, 2,2′‐pyridyl benzimidazole (PBI) catalysed by solvent molecules (H 2 O and CH 3 OH) [21–22] . In the PBI‐H 2 O and PBI‐CH 3 OH complexes, the major deactivation channel was the solvent‐to‐chromophore ESPT process and the assignement was done by measuring the energy barrier of the process in the excited state.…”

“…Here, a proton transfer reaction (ESPT) can be verified by the charge accumulation on the deprotonated solvent species along the reaction pathway. Otherwise, the reaction must be following an H‐atom transfer (ESHT) pathway [21,22] . Until now, solvent assisted tautomerization via ESHT of nucleobase analogue 7‐azaindole have been extensively studied in the gas phase using various spectroscopic methods [24,32–38] …”

“…Recently, experimental investigations aided by computational calculations proposed a novel deactivation mechanism in the excited biomimetic molecule, 2,2'-pyridyl benzimidazole (PBI) catalysed by solvent molecules (H 2 O and CH 3 OH). [21][22] In the PBI-H 2 O and PBI-CH 3 OH complexes, the major deactivation channel was the solvent-to-chromophore ESPT process and the assignement was done by measuring the energy barrier of the process in the excited state. In the case of 27DAI-(H 2 O) 1-3 complexes, a very similar deactivation channel via ESPT was reported.…”

“…Otherwise, the reaction must be following an H-atom transfer (ESHT) pathway. [21,22] Until now, solvent assisted tautomerization via ESHT of nucleobase analogue 7-azaindole have been extensively studied in the gas phase using various spectroscopic methods. [24,[32][33][34][35][36][37][38] Lately, Chou et al have highlighted the importance of the N(2) insertion on the photophysical properties of the azaindole derivatives in the solvated systems.…”