Electronic structure of some penta-atomic heterocyclic molecules studied by gas-phase HeI and HeII photoelectron spectroscopy

Andreocci, M.V.; Cauletti, C.; Sestili, L.

doi:10.1016/0584-8539(84)80138-5

Cited by 15 publications

(7 citation statements)

References 12 publications

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“…The calculations predict that the oxo/thione form (R1) is 5.2 kcal mol -1 more stable than the oxo/thiol form R4. These results are in agreement with the previous results, [5][6][7][8]27,28 The protonated and deprotonated oxo/ thione forms P2b and D1 are thermodynamically more stable than the protonated and deprotonated oxo/thiol forms P4a and D3 by 2.5 and 4.6 kcal mol Our results show that the neutral oxo/thiol forms R4 and R5 are more stable other neutral enol/thione and enol/thiol forms; implying that the hydrogen atom during the 1,3-H transfer process prefers to migrate to heteroatom of the thiocarbonyl group (C2=S7) than that of the other heteroatom of the carbonyl group (C2=O6). These results can be explained in terms of the higher polarizability and consequently the size of the sulfur atom than of the oxygen atom.…”

Section: Relative Stabilitysupporting

confidence: 83%

“…Of particular interest is their ability to donate electrons toward metal ions, which makes them suitable as ligands in the complexation reaction for use in analytical chemistry as sensitive reagents for the analysis of heavy metals 3,4 . Recently, tautomerization of rhodanine family have been theoretically and experimentally studied [5][6][7][8] . These studies suggested that the dioxo, dithione, oxo/thione and thione/oxo derivatives are the predominant form.…”

Section: Introductionmentioning

confidence: 99%

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Tautomeric Study of Neutral, Protonated and Deprotonated Isorhodanine Based on High Level Density Functional Theory

Safi¹

2016

Orient. J. Chem

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High level Density Functional Theory (DFT) using B3LYP/6-311++G(2df,2p)//6-311+G(d,p) calculations on the relative stabilities and structures of the neutral, protonated and deprotonated isorhodanine tautomeric forms are reported in the gas phase and solution. Gas phase and solution B3LYP calculations predict that the oxo/thione tautomer is the most stable one in all cases. Comparison of the gas phase results, bond lengths, bond angles and relative energies, with those of the solution reveals very strong linear relationships. Results of the calculated proton affinities (PAs), molecular gas phase basicity (GBs) and deprotonation enthalpies (DH dep ) indicate that isorhodanine behaves as a sulfur base. The isomerization processes leading from the most stable species to the less stable ones are also investigated.

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Section: Relative Stabilitysupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Tautomeric Study of Neutral, Protonated and Deprotonated Isorhodanine Based on High Level Density Functional Theory

Safi¹

2016

Orient. J. Chem

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“…Tautomerism of Thiazolidine-2,4-dione (Scheme 1) has received a great extensive experimental (Form et al, 1975) and theoretical studies (Tahmassebi, 2003;El-Gogary et al, 2002;Andreocci et al, 1984;Enchev et al, 2002Enchev et al, , 1994Spassova and Enchev, 2004;Ray et al, 2008). All of these studies showed that the predominant tautomer is the thiazolidine-2,4-dione form (diketo tautomer) and there was no evidences supporting thiazoline (oxo-enol) form (Scheme 1).…”

Section: Introductionmentioning

confidence: 94%

A theoretical study on the structure of thiazolidine-2,4-dione and its 5-substituted derivatives in the gas phase. Implications for the thiazolidine-2,4-dione -water complex

Safi

2016

Arabian Journal of Chemistry

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The results of a detailed DFT (B3LYP) investigation on five tautomers of thiazolidine-2,4-dione and their 5-substituted derivatives (ACH 3 , ANH 2 , ACl, AF, ACN-and NO 2 ) are presented here. The energy, geometrical parameters, topological parameters of all species in the gas phase have been calculated at B3LYP6-311++G(3df,2p)//B3LYP/311 + G(d,p) level of theory. The proton affinities (Pas), molecular electrostatic potential (MEP), natural valence atomic orbital energies (NNAO) of the basic center exist in the title compound in the gas phase have been calculated at the same level of theory. The specific hydration of the title compound by one water molecule has been also investigated at the same level of theory. Among the thiazolidine-2,4-dione tautomers and its derivatives, the most stable tautomer corresponds to the diketo forms (A), regardless of the substituent type. Results reveal that the oxygen atom of the carbonyl group at position 2 is more basic than the one at position 4. The existence of different hydrogen bond donor and acceptor centers in these molecules led to different kinds of intermolecular hydrogen bonds (CHAEAEAEO, NAHAEAEAEO and C‚OAEAEAEH) and different kinds of complexes. The stability of the cyclic complexes has been investigated using the analysis of Natural Bond Orbital (NBO), Atoms In Molecules topology, and the thermodynamic data. Results suggest that the water molecule prefers to bind with the oxygen atom, which has low intrinsic character. ª 2015 The Author. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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“…6). Partial theoretical investigations of the tautomer A were carded out [7] by the CNDO/2 method. The aim of the present study was to elucidate the structure and relative stabilities of rhodanine tautomers.…”

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confidence: 99%

Tautomerism of rhodanine

1994

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Semiempirical (MINDO/3, AM1, PM3, MNDO) and ab initio (4-31G and 4-31G + dAO/S basis sets) calculations on the relative stabilities and structures of the five potential tautomeric forms of rhodanine are reported. It is shown that all methods (excepting PM3) predict as most stable 2-thioxo-4-thiazolidinone. These results correspond to the known experimental data. The infrared spectrum of rhodanine was recorded for the region 4000-150 cm -I, and the characteristic bands were compared with AM1 and 4-31G + dAO/S calculated frequencies. The transition states between five pairs of all possible tautomeric forms of the rhodanine were found by the AM I method.KEY WORDS: Tautomerism; rhodanine; IR spectra; ab initio calculations. INTRODUC'IIONRhodanines are used as vulcanizing agents, pharmaceuticals, and intermediates in the synthesis of dyes. The absorption spectra of rhodanine have been studied in connection with interesting photosensibilizing and physiological properties of some 4-thiazolidone derivatives [1]. Another interesting aspect of the chemistry of these compounds is their donor ability toward metal ions, which makes them suitable as ligands in coordination compounds [2]. Rhodanine and its derivatives are used as highly sensitive reagents for the element of the Pt group [3] and selective reagents for Pb and Hg [4,5]. The rhodaaine itself may theoretically exist in five tautomeric forms: A (2-thioxo-4-thiazolidinone), B (4-hydroxy-2(SH)-thiazolethione), C (2-mereapto-4(5H)-thiazolone), D (4-hydroxy-2 (3H)-thiazolethione), and E (2-mercapto-4-thiazolol), which are shown in Fig. 1.The tautomerism of rhodanine was studied experimentally by different authors (see the quotations in Ref. 6). Partial theoretical investigations of the tautomer A were carded out [7] by the CNDO/2 method. The aim of the present study was to elucidate the structure and relative stabilities of rhodanine tautomers. There are no experimental data on the structure of tautomers B-E. Calculations were done using ab initio and semiempirical methods. Our main purpose was to determine the reliability of lhe theoretical results by comparing them with experimental data. In this work we also present a theoretical investigation on the IR spectrum of the rhodanine with quantum chemical methods. The intramolecular proton transfer reactions between the possible tautomeric forms were studied by the AM1 method. COMPUTATIONAL DETAILSIn the study of the different tautomeric forms of rhodanine, the semiempirical MINDO/3 [8], PM3 [9], MNDO [10,11], and AM1 [12, 13] methods were used. The calculations were carried out with the MOPAC 6.0 program package [14]. The geometries of the investigated compounds were completely optimized using the EF [15] procedure. Recently, Reynolds [16] has shown a close correspondence between the AM1 and HF/6-31G* potential surfaces, indicating that the AMt and high-level ab initio results for geometries at energy minima and transition states are in good agreement. For this 225

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Electronic structure of some penta-atomic heterocyclic molecules studied by gas-phase HeI and HeII photoelectron spectroscopy

Cited by 15 publications

References 12 publications

Tautomeric Study of Neutral, Protonated and Deprotonated Isorhodanine Based on High Level Density Functional Theory

Tautomeric Study of Neutral, Protonated and Deprotonated Isorhodanine Based on High Level Density Functional Theory

A theoretical study on the structure of thiazolidine-2,4-dione and its 5-substituted derivatives in the gas phase. Implications for the thiazolidine-2,4-dione -water complex

Tautomerism of rhodanine

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