Slow proton transfer dynamics of a four member intramolecular hydrogen bonded isoindole fused imidazole system: A spectroscopic approach to photophysical properties

Simple practical method for synthesis of trisubstituted imidazoles: an efficient copper catalyzed multicomponent reaction

A rapid practical process has been developed for synthesis of 2,4,5-trisubstituted-imidazoles in excellent yields up to 95% from readily available starting materials. In this CuI catalyzed synthesis, trisubstituted imidazoles were afforded in short reaction times, wherein the substrate scope is well explored with benzoin as well as benzil reacting with different aldehydes in the presence of ammonium acetate as the nitrogen source.

Excited-State Intramolecular Proton Transfer: A Short Introductory Review

In this short review, we attempt to unfold various aspects of excited-state intramolecular proton transfer (ESIPT) from the studies that are available up to date. Since Weller’s discovery of ESIPT in salicylic acid (SA) and its derivative methyl salicylate (MS), numerous studies have emerged on the topic and it has become an attractive field of research because of its manifold applications. Here, we discuss some critical aspects of ESIPT and tautomerization from the mechanistic viewpoint. We address excitation wavelength dependence, anti-Kasha ESIPT, fast and slow ESIPT, reversibility and irreversibility of ESIPT, hydrogen bonding and geometrical factors, excited-state double proton transfer (ESDPT), concerted and stepwise ESDPT.

Theoretical insights into excited-state hydrogen bonding effects and intramolecular proton transfer (ESIPT) mechanism for BTS system

In this work, N,N'-bis(salicylidene)-(2-(3',4'-diaminophenyl)benzothiazole) (named as "BTS") system was studied about its excited-state intramolecular proton transfer (ESIPT) process. The analyses about reduced density gradient (RDG) reveal the formation of two intramolecular hydrogen bonds in BTS system. Bond lengths and angles, infrared (IR) vibrations as well as frontier molecular orbitals (MOs) using TDDFT method indicate that the strength of hydrogen bond should be enhanced in the S1 state. Particularly, hydrogen bond O1-H2···N3 undergoes larger variations compared with O4-H5···N6, which infers that hydrogen bond O1-H2···N3 may play a decisive role in the ESIPT process of BTS system. Given the two hydrogen bonds of BTS molecule, two types of potential energy curves have been constructed, which confirms that only single proton transfer process occurs due to lower energy barrier along with O1-H2···N3 rather than O4-H5···N6. This work not only presents a reasonable explanation for previous experiment, but also clarifies the specific ESIPT mechanism for BTS system.

Modulation of Excited State Proton Transfer Dynamics of a Lactim-Lactam Tautomeric System in Different Block Copolymer-Surfactant Aggregates

The proton transfer (PT) process in 1-(2-hydroxy-5-chloro-phenyl)-3,5-dioxo-1H-imidazo-[3,4-b]isoindole (ADCL) has been studied in three different copolymer-surfactant supramolecular assemblies prepared in aqueous 1% P123 triblock copolymer micellar solution with varying concentrations of surfactants (sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and triton-X-100 (TX 100)). The aim of the present study is to monitor the modulation of the PT process by changing the degree of micellar hydration inside the P123 micelle with the addition of the three different surfactants (two ionic and one non ionic), that is, in P123-surfactant aggregates. Besides, a comparative study has been done with these results with those in water, pure P123 micellar medium and three different surfactants medium. The micropolarity measurement and time-resolved fluorescence anisotropic measurements have been performed to evaluate the binding location of the probe (ADCL) in the three different copolymer-surfactant supramolecular assemblies. It is found that the micropolarity at the binding site of the molecule in the various environments largely influences the PT rate of ADCL. The PT rate is found to be the slowest in the P123 medium and in P123-surfactant aggregates the rate becomes faster as the micropolarity around the binding locations of the molecule in these aggregates is higher in comparison to that in P123 micelle.