Spectroscopic characterization of hydrogen-bonded proton transfer complex between 4-aminopyridine with 2,6-dichloro-4-nitrophenol in different solvents and solid state

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• 作者：Khairia M. Al-Ahmary^a ; Eman A. Al-Solmy^a ; Moustafa M. Habeeb^a ; ^b ; ^{mostafah2002@yahoo.com" class="auth_mail}
• 关键词：Spectroscopy ; Proton transfer ; GAMESS computations ; Molecular modeling
• 刊名：Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
• 出版年：21 May, 2014
• 年：2014
• 卷：126
• 期：Complete
• 页码：260-269
• 全文大小：1999 K

文摘

Proton transfer reaction between the proton donor 2,6-dichloro-4-nitrophenol (DCNP) with the proton acceptor 4-aminopyridine (4APy) has been investigated spectrophotometrically in different solvents included the aprotic solvent acetonitrile (MeCN), the protic one methanol (MeOH) and a mixture consists of 50% acetonitrile + 50% dichloroethane (ANDC). The proton transfer complex is produced instantaneously with deep yellow color and absorption maxima in the range 395-425 nm. The composition of the complex was characterized spectrophotometrically to be 1:1 in all solvent proving that the solvent has no effect on the complex stoichiometry. The proton transfer formation constant has been estimated by using Benesi-Hildebrand equation where the highest value was recorded in the mixture ANDC. This proofs the high stability of the complex in less polar solvent as a result of the high stability of the complex ground state. The solid complex has been synthesized and characterized by elemental analysis to be 1:2 [(proton donor) (proton acceptor)₂]. The obtained solid complex was analyzed by infrared spectroscopy where two broad band鈥檚 at 3436 and 2500 cm^鈭? characterized for asymmetric NHN⁺ hydrogen bond were identified. Molecular modeling utilizing GAMESS computations as a package of ChemBio3D Ultra12 program was carried out where asymmetric NHN⁺ was explored with NN bond distance 2.77 脜. The computations showed a difference in molecular geometry of the complex compared with reactants especially bond lengths, bond angles and distances of close contact.