Study of O -H O bonded-cyclic dimer for 2,5-Dihydroxyterephthalic acid as aided by MD, DFT calculations and IR, Raman, NMR spectroscopy

Molecular Dynamics-simulated O -H center dot center dot center dot O bonded-cyclic dimer structure, called D c , has been proposed for 2,5-Dihydroxyterephthalic acid - a potential organic linker in Hydrogen-bonded Organic Frameworks (HOF). Among many dimer species bound by inter-molecular O -H center dot center dot center dot O bonds, D c was chosen because of its relatively highest lifetime of 18.3 ps as indicated by the radial distribution functions (RDF). Experimentally observed intense but broad down-shifted IR absorptions peak at similar to 3023 cm -1 and bands near 2556 cm -1 combined with staggered occurrence of IR and Raman bands in other spectral regions suggested that the proposed cyclic dimer appeared to possess an extended quasi - centrosymmetric configuration. Upon optimization of D c at B3LYP/6-311 ++ G(d,p) level, it yielded geometry and vibrational spectra in agreement with experimental spectra. Further, we have characterized both intra- and inter-molecular O -H center dot center dot center dot O bonds in D c using stabilization energy E (2) and other molecular orbital (MO) properties from NBO analysis. Bond critical points (BCPs) and ring critical points (RCPs) deduced from electron density ( rho( r )), its laplacian ( V 2 rho(r) ) and potential energy density (v( r )) using AIM calculations have provided complementary perspectives. Additionally, a combination of quantitative analysis and graphical visualization of the charge regions where non-covalent interactions occur in real space - intra- and inter-molecular O -H center dot center dot center dot O bonds, van der Waals and repulsive steric clash interactions have been obtained from NCI calculations. (c) 2022 Elsevier B.V. All rights reserved.