Evaluation of weak intermolecular interactions in molecular crystals via experimental and theoretical charge densities

Analysis of charge density distributions in molecular crystals has received considerable attention in the last decade both from high-resolution X-ray diffraction studies and from high-level theoretical calculations. An overview of the progress made in deriving one-electron properties, intermolecular interactions in terms of the Atoms in Molecule (AIM) approach (R.F.W. Bader. Atoms in Molecules-A Quantum Theory, Clarendon, Oxford (1990), R.F.W. Bader. J. Phys. Chem., A102, 7314 (1998)) is given with special emphasis on improvements in charge density models and development of both experimental and theoretical techniques to interpret and analyse the nature of weak intermolecular interactions. The significance of the derived results from the charge density of coumarin and its derivatives have been analysed to obtain insights into the nature of intermolecular C-H…O, C-H…π, π…π, C-H…S, and S…S contacts. The appearance of a 'region of overlap' to segregate hydrogen bonds from van der Waals interactions based on the criteria proposed by Koch and Popelier (U. Koch, P.L.A. Popelier. J. Phys. Chem., 99, 9747 (1995), P.L.A. Popelier. Atoms in Molecules. An Introduction, pp. 150-153, Prentice Hall, UK (2000)) and the identification of differences in energy surfaces in concomitant polymorphs of 3-acetylcoumarin are described

Solvent mediated centric/non-centric polymorph pairs of an indole derivative: subtle variation of C-HO hydrogen bonds and C-Hπ interactions

Centric (P21/n) and non-centric (P21) polymorphic pairs of biologically active 1-(4-fluorophenyl)-6,6-dimethyl-2-phenyl-1,5,6,7-tetrahydro-4H-indol-4-one crystallized from different solvents have been elucidated via single crystal and powder X-ray diffraction studies, morphological observations and calorimetric measurements. C-H...O hydrogen bonding and weak intermolecular C-H...π interactions generate distinct packing features in the two forms

Synthesis, structure and ionic conductivity in scheelite type Li_0.5Ce_0.5-xLn_xMoO₄ (x = 0 and 0.25, Ln = Pr, Sm)

Scheelite type solid electrolytes, Li0.5Ce0.5-xLnxMoO4 (x = 0 and 0.25, Ln = Pr, Sm) have been synthesized using a solid state method. Their structure and ionic conductivity (σ) were obtained by single crystal X-ray diffraction and ac-impedance spectroscopy, respectively. X-ray diffraction studies reveal a space group of I41/a for Li0.5Ce0.5-xLnxMoO4 (x = 0 and 0.25, Ln = Pr, Sm) scheelite compounds. The unsubstituted Li0.5Ce0.5-xLnxMoO4 showed lithium ion conductivity ∼10−5-10−3 Ω−1cm−1 in the temperature range of 300-700°C (σ = 2.5 × 10−3 Ω−1cm−1 at 700°C). The substituted compounds show lower conductivity compared to the unsubstituted compound, with the magnitude of ionic conductivity being two (in the high temperature regime) to one order (in the low temperature regime) lower than the unsubstituted compound. Since these scheelite type structures show significant conductivity, the series of compounds could serve in high temperature lithium battery operations