Abstract
Cocrystals of 4,4'-bipyridyl and several carboxylic acids were grown from the methanol solution of the cocrystal formers. Complete (14)N NQR spectra of these cocrystals have been measured using (1)H-(14)N nuclear quadrupole double resonance. The principal values of the quadrupole coupling tensor are calculated from the (14)N NQR frequencies. A large variation in the (14)N quadrupole coupling constant between 1.3 MHz and 4.7 MHz is observed. A very low (14)N quadrupole coupling constant, characteristic for proton transfer O-H···N → O(-)···H-N(+), is observed in 4,4'-bipyridyl-oxalic acid (1 : 1). In 4,4'-bipyridyl-5-chlorosalycilic acid (1 : 1) the (14)N NQR data show the presence of a short, strong N···H···O hydrogen bond. A correlation of the principal values of the (14)N quadrupole coupling tensor is observed. The correlation is analyzed in the model, where the deformation of the lone pair electron orbital and the change of the population of the π-electron orbital produce the variation of the (14)N quadrupole coupling tensor in the hydrogen bonded 4,4'-bipyridyl. The temperature variation of the (14)N quadrupole coupling tensor in 4,4'-bipyridyl-5-chlorosalycilic acid (1 : 1) is analyzed. Proton displacement within the N···H···O hydrogen bond and the change of the population of the π-electron orbital at the two nitrogen positions in a 4,4'-bipyridyl molecule in the temperature interval between 157 K and 323 K are determined.
Highlights
Crystal engineering is the understanding of intermolecular interactions in the context of crystal packing and the utilization of such understanding in the design of new solids with desired physical, chemical and pharmaceutical properties.[1]
In the present paper we present the results of Nuclear quadrupole resonance (NQR) investigation of cocrystals of BPY and benzoic acid (BA), 5-chlorosalycilic acid (5CSA), 4-hydroxybenzoic acid (4HBA), oxalic acid (OXA) and malonic acid (MA)
The frequencies in the first set are close to the 14N NQR frequencies observed in solid pyridine[23] and may be assigned to the nonhydrogen bonded nitrogen position
Summary
Hydrogen bonding and proton transfer in cocrystals of 4,40-bipyridyl and organic acids studied using nuclear quadrupole resonance. A very low 14N quadrupole coupling constant, characteristic for proton transfer O–HÁ Á ÁN - OÀÁ Á ÁH–N+, is observed in 4,40-bipyridyl–oxalic acid (1 : 1). A correlation of the principal values of the 14N quadrupole coupling tensor is observed. The correlation is analyzed in the model, where the deformation of the lone pair electron orbital and the change of the population of the p-electron orbital produce the variation of the 14N quadrupole coupling tensor in the hydrogen bonded 4,40-bipyridyl. Proton displacement within the NÁ Á ÁHÁ Á ÁO hydrogen bond and the change of the population of the p-electron orbital at the two nitrogen positions in a 4,40-bipyridyl molecule in the temperature interval between 157 K and 323 K are determined
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
