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Metal Ion Directed Tautomeric Polymorphism in a Hydrazonamide/Hydrozonate System
Author(s) -
Mandal Arkalekha,
Patel Bhisma K.
Publication year - 2017
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201601432
Subject(s) - tautomer , chemistry , methylene , hydrogen bond , hydrazide , natural bond orbital , benzoic acid , amide , intramolecular force , ligand (biochemistry) , stereochemistry , medicinal chemistry , density functional theory , molecule , computational chemistry , organic chemistry , receptor , biochemistry
Ortho and para ‐aminophenyl substituted hydrazonamide ligands viz . 2‐amino‐benzoic acid (amino‐pyridin‐2‐yl‐methylene)‐hydrazide and 4‐amino‐benzoic acid (amino‐pyridin‐2‐yl‐methylene)‐hydrazide) can exist in two tautomeric forms. The hydrazonamide (keto) form of the former ligand is only observed in free ligand, while its enolate form exists in some of its metal complexes. Both hydrazonamide and hydrazonate tautomers possess a six membered intramolecular hydrogen bond between the o ‐amino group and amide oxygen or imino nitrogen respectively. As a result, hydrazonamide and hydrazonate tautomeric forms exist in different molecular conformation and thus ‘tautomeric polymorphism’ is observed in this system. The evidence of tautomerism and consequent conformational change in metal complexes of 2‐amino‐benzoic acid (amino‐pyridin‐2‐yl‐methylene)‐hydrazide is well supported by both DFT and NBO studies.