title: Spectroscopic characterization of hydrogen-bonded proton transfer complex between 4-aminopyridine with 2,6-dichloro-4-nitrophenol in different solvents and solid state.
abstract: 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 395-425nm. 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's at 3436 and 2500cm(-1) 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 2.77Å. The computations showed a difference in molecular geometry of the complex compared with reactants especially bond lengths, bond angles and distances of close contact.
authors.affiliation: Chemistry Department, Sciences Faculty for Girls, King Abdulaziz University, Jeddah, Saudi Arabia.
authors.forename: Khairia M
authors.initials: KM
authors.lastname: Al-Ahmary
authors.affiliation: Chemistry Department, Sciences Faculty for Girls, King Abdulaziz University, Jeddah, Saudi Arabia.
authors.forename: Eman A
authors.initials: EA
authors.lastname: Al-Solmy
authors.affiliation: Chemistry Department, Sciences Faculty for Girls, King Abdulaziz University, Jeddah, Saudi Arabia; Chemistry Department, Faculty of Education, Alexandria University, Alexandria, Egypt. Electronic address: mostafah2002@yahoo.com.
authors.forename: Moustafa M
authors.initials: MM
authors.lastname: Habeeb
mesh_terms: D015761:4-Aminopyridine / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D009596:Nitrophenols / Q000737:chemistry*; D011522:Protons; D012997:Solvents / Q000737:chemistry; D013053:Spectrophotometry
chemical_list: D009596:Nitrophenols; D011522:Protons; D012997:Solvents; C015802:2,6-dichloro-4-nitrophenol; D015761:4-Aminopyridine
keywords: GAMESS computations; Molecular modeling; Proton transfer; Spectroscopy