Role of rotamerisation and excited state intramolecular proton transfer in the photophysics of 2-(2′-hydroxyphenyl)benzoxazole, 2-(2′-hydroxyphenyl)benzimidazole and 2-(2′-hydroxyphenyl)benzothiazole: a theoretical study

Intra- and intermolecular proton transfer in methyl-2-hydroxynicotinate

“…Ground state geometry of all the species were fully optimized using AM1 method (QCMP137, MOPAC6/PC) [33] and the coordinates observed by PCMODEL [34]. As suggested and found by others [21,22,[35][36][37][38], this method provides acceptable approximations to give results, which are quite close to experimental results. Total energy (E) relative to the most stable structure, heats of formation (DH f ), dipole moment (m) dihedral angle (j) and charge density at each basic center as compared to the neutral atom have been compiled in Table 1.…”

“…Further, activation barrier for the conversion of P to T form decreased in S 1 state from 109.2 to 76.4 kJ mol À1 . Although activation barrier in S 1 state is still quite large as compared to those determined experimentally for similar systems [21,38,53], decrease in the barrier height in S 1 state suggests that kinetically ESIPT will be more favorable in S 1 state as compared to that in S 0 state. Similar discrepancy is also observed between the experimental and calculated activation barrier [21,38,53] in some other molecules.…”

“…Although activation barrier in S 1 state is still quite large as compared to those determined experimentally for similar systems [21,38,53], decrease in the barrier height in S 1 state suggests that kinetically ESIPT will be more favorable in S 1 state as compared to that in S 0 state. Similar discrepancy is also observed between the experimental and calculated activation barrier [21,38,53] in some other molecules. Beside the high activation barrier in S 1 state, low F f of the tautomer emission in MEHNA could be due smaller IHB strength (3.9 kJ mol À1 ) in P form as compared to that observed in salicylic acid (46 kJ mol À1 ) [54] and in 1-hydroxy-9-fluorenone (20.6 kJ mol À1 ) [55].…”

Electronic and photophysical properties of 2-(2′-hydroxyphenyl)benzoxazole and its derivatives enhancing in the excited-state intramolecular proton transfer processes: A TD-DFT study on substitution effect

“…The photophysics of HBO as the parent compound in our present work has been widely studied experimentally [1,2,5,7,9,18,[21][22][23][24] and theoretically [25][26][27][28][29][30][31][32][33][34][35] because of its structural simplicity and easily chemical modification. Thus, its derivatives [14,25,31,[36][37][38] have also been increasingly investigated both in experiment and theoretical studies.…”

New fluorescent monomers and polymers displaying an intramolecular proton‐transfer mechanism in the electronically excited state (ESIPT). IV. Synthesis of acryloylamide and diallylamino benzazole dyes and its copolymerization with MMA

“…[1][2][3][4][5] This phenomenon has implications in the UV-light stabilizers field, 6,7 laser dyes, 8 new polymeric materials, 9 -12 and also as fluorescent probes to labeling proteins. 13,14 The ESIPT mechanism is quite dependent on the solvent polarity, [15][16][17] and many studies regarding this dependence, [17][18][19][20][21] as well as, theoretical calculations involving the geometry of the conformers in solution [22][23][24][25][26][27] have been made. In protic and/or polar solvents the enol-cis open conformer (E II ) can be stabilized by intermolecular hydrogen bond with the solvent.…”