Photoinduced intramolecular charge transfer in trans-2-[4′-(N, N-dimethylamino)styryl]imidazo[4,5- b]pyridine: effect of introducing a C=C double bond

Abstract

The spectral characteristics of trans-2-[4'-(N,N-dimethylamino)styryl]imidazo[4,5-b]pyridine (t-DMASIP-b) have been investigated using absorption and fluorescence techniques, and compared with 2-(4'-N,N-dimethylamino)imidazo[4,5-b]pyridine (DMAPIP-b). The study reveals that introduction of a C[double bond, length as m-dash]C double bond strongly perturbs the photophysics of the system. Unlike DMAPIP-b, t-DMASIP-b emits a single emission in aprotic and protic solvents. The emission occurs from the locally excited state in nonpolar solvents and from a planar intramolecular charge transfer (PICT) state in polar solvents. Multiple linear regression analysis suggests that among the different solvent parameters, the dipolar interaction contributes more to the stabilization of the system in both the ground and excited states. Theoretical calculations suggest that, unlike in DMAPIP-b, proton coupled twisted intramolecular charge transfer (TICT) emission does not occur in t-DMASIP-b. The higher quantum yield obtained in the viscous solvent glycerol is attributed to the restriction of the twisting of the olefinic bond. The photoirradiation of t-DMASIP-b shows that isomerization takes place in all solvents, including viscous glycerol. The theoretically simulated potential energy surface shows that isomerization occurs via a phantom state, which is a nonradiative process. The rise in temperature favors the photoisomerization, thus, the fluorescence quantum yield decreases. The prototropic study indicates that, unlike in DMAPIP-b, the protonation takes place at different places to form the monocations.

Rapid screening and scale‐up of ultracentrifugation‐free, membrane‐based procedures for purification of His‐tagged membrane proteins

“…Thus, OM and DMNG were not further investigated for KR2 purification. Our findings indicate that the hydrophobicity of the detergent micelles in different sodium salt solutions increases in the order CH 3 COO − < Br − < Cl − , which agrees with the salting‐out effect and concentration of the extracted protein (Figure ); although the amounts of protein extracted in NaBr and NaCl solutions are statistically indistinguishable. The micelles in CH 3 COO − show only slightly lower hydrophobicity than micelles in Br − and yet extract significantly less protein.…”

“…In an earlier study, we hypothesized that higher micelle hydrophobicities promote partitioning of the hydrophobic MPs into the micelles . The detergent micelle hydrophobicity was determined by a fluorescence‐based assay from our previous work . To facilitate protein analysis, we extracted the MP, Krokinobacter eikastus rhodopsin 2 (KR2) from E. coli cells using the detergents DM and DDM in a variety of salts and salt concentrations.…”

“…21,[37][38][39] The detergent micelle hydrophobicity was determined by a fluorescence-based assay from our previous work. 30,35,40,41 To facilitate protein analysis, we extracted the MP, Krokinobacter eikastus rhodopsin 2 (KR2) from E. coli cells using the detergents DM and DDM in a variety of salts and salt concentrations. The high extinction coefficient of KR2 at 525 nm is a unique feature that enables its quantification without interference from contaminant proteins.…”

Formation of a Nonlinear Optical Host–Guest Hybrid Material by Tight Confinement of LDS 722 into Aluminophosphate 1D Nanochannels

“…However,t hey are very flexible molecules and requirev ery rigid environments to restricttheir molecular motion in order to achieveh igh fluorescence or lasing efficiency; [31] indeed, rotational motions aroundt he different bonds are responsible for the non-radiative deactivation, such as trans-cis isomerization,o re specially the formation of twisted intramolecular charge transfer (TICT) states, usually non-fluorescent. [32] In this sense, at ight confinement of these molecules in 1D nanoporous hosts becomes crucial.I nterestingly,h emicyanine dyes usually exhibit high solubility, and hight hermala nd chemicals tability to withstand the severe conditions of the hydrothermal crystallizationo ft he zeolitic nanoporous host.…”

Femto- to Millisecond Time-Resolved Photodynamics of a Double-Functionalized Push–Pull Organic Linker: Potential Candidate for Optoelectronically Active MOFs

“…On the contrary, the Stokes-shift value in non-protic and methanol solvents exhibits a strong dependence with their orientation polarizability (∆f ), having values ranging between 0.162 and 0.333 ( Table 1). The Stokes-shift values and the orientation polarizability of the non-protic solvents have been correlated using the Lippert-Mataga equation [34][35][36][37]:…”