Excited-State Intramolecular Proton Transfer in 2-(2-Hydroxyphenyl)benzimidazole and -benzoxazole: Effect of Rotamerism and Hydrogen Bonding

Das, Kaustuv; Sarkar, Nilmoni; Ghosh, Ajit; Majumdar, D.; Nath, Dilip C.; Bhattacharyya, Kankan

doi:10.1021/j100088a006

Cited by 268 publications

(230 citation statements)

References 3 publications

(2 reference statements)

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“…Considering that the calculations are semiempirical (AM1), the agreement between the calculated data and the crystallographic ones are reasonably good. Table 2 [16]. Figure 3 indicates the existence of only one stable form of HBT in the ground state, the normal (I) one.…”

Section: Resultsmentioning

confidence: 99%

“…In organic bifunctional molecules, containing both the hydrogen atom donor and acceptor groups in close proximity, an intramolecular hydrogen bond is generally formed in the ground electronic state [15]. A distance of < 2 Å between the donor and the acceptor atom favours the migration of the proton to produce a phototautomer in the excited state [16]. The ESIPT process is extremely fast occurring within subpicosecond time scale that falls within the range of the period of low frequency vibrations.…”

Section: Introductionmentioning

confidence: 99%

“…They have also calculated the molecular geometry of the excited enol and keto forms using the MNDO methods [36]. Effect of rotamerism and hydrogen bonding on the ESIPT in HBO and HBI has also been studied using steadystate and time-resolved emission spectroscopy at various temperatures and by semi-empirical quantum mechanical methods like CNDO/SCI and AM1 [16,37].…”

Section: Introductionmentioning

confidence: 99%

“…However, experiments suggest that upon excitation only the normal form (I in scheme 1) undergoes ESIPT to give the corresponding tautomer resulting in an emission with a large stokes shift [39]. The rotamer (II in scheme 1) does not undergo ESIPT reaction and its short wavelength emission shows a mirror image relation with the corresponding absorption [16]. The excitation spectra of the rotamer and the tautomer emission show a large change in their relative intensities with a change in temperature.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical Modelling for the Ground State Rotamerisation and Excited State Intramolecular Proton Transfer of 2-(2’-hydroxyphenyl)oxazole, 2-(2’-hydroxyphenyl)imidazole, 2-(2’-hydroxyphenyl)thiazole and Their Benzo Analogues

Purkayastha

Chattopadhyay

2003

IJMS

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Two series of compounds, one comprising of 2-(2′-hydroxyphenyl)benzoxazole (HBO), 2-(2′-hydroxyphenyl)benzimidazole (HBI), 2-(2′-hydroxyphenyl)benzothiazole (HBT), and the other of 2-(2′-hydroxyphenyl)oxazole (HPO), 2-(2′-hydroxyphenyl)imidazole (HPI) and 2-(2′-hydroxyphenyl)thiazole (HPT) are susceptible to ground state rotamerization as well as excited state intramolecular proton transfer (ESIPT) reactions. Some of these compounds show experimental evidence of the existence of two ground state conformers. Out of these two one undergoes ESIPT reaction leading to the formation of the tautomer. The two photophysical processes, in combination, result in the production of a number of fluorescence bands each one of which corresponding to a particular species. Semiempirical AM1-SCI calculations have been performed to rationalize the photophysical behaviour of the compounds. The calculations suggest that for the first series of compounds, two rotational isomers are present in the ground state of HBO and HBI while HBT has a single conformer under similar circumstances. For the molecules of the other series existence of rotamers depends very much on the polarity of the environment. The potential energy curves (PEC) for the ESIPT process in different electronic states of the molecules have been generated theoretically. The simulated PECs reveal that for all these systems the IPT reaction is unfavourable in the ground state but feasible, both kinetically and thermodynamically, in the S 1 as well as T 1 states.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Theoretical Modelling for the Ground State Rotamerisation and Excited State Intramolecular Proton Transfer of 2-(2’-hydroxyphenyl)oxazole, 2-(2’-hydroxyphenyl)imidazole, 2-(2’-hydroxyphenyl)thiazole and Their Benzo Analogues

Purkayastha

Chattopadhyay

2003

IJMS

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“…Oxa and Oxa-ester have metal binding moieties and photoresponsive 2-(2 0 -hydroxyphenyl)benzoxazole (HBO) skeleton in its structure. HBO is well known as a typical molecule, which undergoes excited state intramolecular proton-transfer (ESIPT) [28][29][30][31][32][33][34][35][36][37][38][39][40][41]. Thus, the produced tautomer has different electronic structure and may have a considerably different binding constant with cations.…”

Section: Introductionmentioning

confidence: 99%

Photochemical and complexation studies for new fluorescent and colored chelator

Ohshima

Momotake

Arai

2005

Science and Technology of Advanced Materials

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The photo-induced intramolecular proton (or hydrogen atom) transfer (ESIPT) and metal binding properties of Oxa-ester were studied in methanol solution. The dissociation constant between Oxa-ester and the metal ion was highly dependent with the metal ion and was determined by Hill plots or iterative least squares fitting to be 447 mM, 14.9 mM, and 290 nM for Ca 2C , Zn 2C , and Cu 2C , respectively, in methanol. The fluorescence intensity of Oxa-ester greatly increased with increasing concentration of Zn 2C , while the fluorescence intensity decreased with the addition of Ca 2C and Cu 2C . Transient absorption spectroscopy revealed that Oxa-ester underwent ESIPT to give Z-NH isomer in the excited state in benzene, while Oxa did not undergo ESIPT probably due to the hydrogen bonding with solvent water. q

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Excited‐State Intramolecular Proton Transfer in 2‐(2′‐Hydroxyphenyl)benzoxazole Derivatives

Pang

2010

Hydrogen Bonding and Transfer in the Excited State

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Excited-State Intramolecular Proton Transfer in 2-(2-Hydroxyphenyl)benzimidazole and -benzoxazole: Effect of Rotamerism and Hydrogen Bonding

Cited by 268 publications

References 3 publications

Theoretical Modelling for the Ground State Rotamerisation and Excited State Intramolecular Proton Transfer of 2-(2’-hydroxyphenyl)oxazole, 2-(2’-hydroxyphenyl)imidazole, 2-(2’-hydroxyphenyl)thiazole and Their Benzo Analogues

Theoretical Modelling for the Ground State Rotamerisation and Excited State Intramolecular Proton Transfer of 2-(2’-hydroxyphenyl)oxazole, 2-(2’-hydroxyphenyl)imidazole, 2-(2’-hydroxyphenyl)thiazole and Their Benzo Analogues

Photochemical and complexation studies for new fluorescent and colored chelator

Excited‐State Intramolecular Proton Transfer in 2‐(2′‐Hydroxyphenyl)benzoxazole Derivatives

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