Muthuraja Perumal - Hydrogen bonded R2 (8) graph set in inducing charge transfer mechanism in guanidinium-3,5-dinitrobenzoate: A combined experimental, theoretical and Hirshfeld surface study

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      Publication Details (including relevant citation   information):

      Journal of Molecular Structure, 2017


      A supramolecular crystal, guanidinium-3,5-dinitrobenzoate (GDNB),   was synthesised and its structure was confirmed by single crystal   X-ray diffraction at 25 °C. Distinct N-H⋯O hydrogen bonding   interactions as well as π-π interactions in GDNB were ascertained   from the crystal structure. An exhaustive Hirshfeld surface   analysis spells out variety of intermolecular contacts in GDNB   proving the existence of a supramolecular isomer at 25 °C.   The N-H⋯O hydrogen bond led to the formation of R2,2(8) graph set   which functions as a bridge for the intermolecular charge   transfer occur in GDNB. Theoretical calculations were carried out   at B3LYP level of theory at 6-311 G(d,p) and cc-pvtz basis   sets using Gaussian 09 software package. FT-IR and FT-Raman   spectral analyses were also carried out to confirm various   functional groups in GDNB. The 1H, 13C and   DEPT-135 NMR spectra of GDNB confirmed the various types and   number of protons as well as carbons in the molecule. A   systematic and complete DFT calculation covering optimisation,   ****-LUMO analysis, CHELPG charge analysis, hyperpolarizability   and Mulliken charge analysis was carried out. There is no   absorption in the entire visible region and the maximum cut off   wavelength of GDNB crystal is 266 nm. The charge transfer   was confirmed by both ****-LUMO and NBO analyses where electrons   are promoted from guanidinium moiety to the 3,5-dinitrobenzoate   through N-H⋯O hydrogen bonds. NBO analysis supports the   interactions of chemical bonds and structural properties of GDNB.   Wiberg bond indices expose the nature of donor and acceptor   moieties. The thermal stability of GDNB was confirmed from TG/DTA   and DSC analyses. The compound is stable up to 250 °C. DFT   calculations of static as well as frequency dependant electro   optic properties were also undertaken. The formation of strong   hydrogen bonded dimer as ring graph set favours the charge   transfer which greatly influences the optical properties of the   compound.

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