Binoy K. Saha

A product of a templated solid-state photodimerization acts as a template: single-crystal reactivity in a single polymorph of a cocrystal.

The concept of using a product of a template-directed solid-state reaction as a template is demonstrated. A cyclobutane lined with four carboxylic acid groups is employed as the template in photoreactive cocrystals. The resulting material is shown to exhibit polymorphism.

The effect of temperature on interhalogen interactions in a series of isostructural organic systems

The thermal expansion behaviors of two sets, the guest-free forms and the ethyl acetate solvates, of interhalogen interaction mediated isostructural networks of 2,4,6-triethyl-1,3,5-tris(4-halophenoxy)methylbenzene (halo = Cl, Br and I) have been studied. In both of the series, the order of increase in interhalogen distances with increasing temperature is I⋯I < Br⋯Br < Cl⋯Cl which is actually the reverse order of interhalogen interaction strength.

Steric guided anomalous thermal expansion in a dimorphic organic system

The thermal expansion behaviour of two polymorphs of 4,4′-methylenebis(2,6-dimethylaniline) (MBDA) has been studied. The monoclinic form exhibits a very large uniaxial negative thermal expansion (αl = −174(8) MK−1) and 1.6 times higher αv than the triclinic form, which exhibits a normal positive thermal expansion. This anomalous thermal expansion behaviour in the monoclinic form is guided by the steric effects of the strongly vibrating methyl groups in the solid.

Can the thermal expansion be controlled by varying the hydrogen bond dimensionality in polymorphs

2-Butynoic acid exists in two enantiotropically related polymorphic forms. The monoclinic form, containing a one dimensional hydrogen bond in the structure, exhibits a smaller volumetric thermal expansion coefficient than the triclinic form which has a zero dimensional hydrogen bond. The phase transformation 1D → 0D has been correlated with the different thermal expansion abilities of the groups present in the molecule and the crystal packing in these two forms.

Hydrogen-bond networks in the binary complexes of trigonal molecules with 4,4′-bipyridine

A 1:1 binary salt and a cocrystal of two chemically different trigonal symmetric donor molecules, 2,4,6-trimethyl-1,3,5-benzenetricarboxylic acid (MTAH3) and 2,4,6-tris(4-hydroxyphenoxy)-1,3,5-triazine (HPT) with 4,4′-bipyridine (bipy) have been synthesized and the crystal structures have been studied. The MTAH3·bipy salt shows an unprecedented parallel interpenetrated 3D bookshelf type of structure aided by C(8) type O–H⋯O and acid⋯pyridine O–H⋯N interactions. The HPT·bipy complex has a 2D → 3D parallel polycatenated pcu net aided by the usual hydroxy⋯pyridine synthon and supported by a C–H⋯O interaction. Both the complexes exhibit the formation of 3D structures from trigonal donors, contrary to the fact that trigonal species generally are being considered to be candidates for construction of 2D networks.

Thermal Expansion in Organic Crystals

Though a large number of thermal expansion studies have been reported on inorganic systems, a considerably large number on metal–organic-based systems, but those on purely organic systems are too few. Moreover, owing to the complexity of the crystal structure of the organic systems, their thermal expansion behaviors are poorly understood. This review focuses on some interesting thermal expansion studies conducted on purely organic crystals and also on some important structure–property relationships of thermal expansion of organic crystals with intermolecular interactions, melting point of systems, guest molecules in inclusion compounds, and hydrogen bond dimensionality in the crystal structures. Most studies discussed here have been reported in recent years.

Comparison of pyridyl and pyridyl N-oxide groups as acceptor in hydrogen bonding with carboxylic acid

Competition experiments between pyridyl and pyridyl N-oxide groups have been performed to find out which of these two groups is a better acceptor in hydrogen bonding with the carboxylic acid group. 4,4′-bipyridine N-monoxide, a rigid, conjugated, and linear molecule and 4,4′-trimethylenebipyridine N-monoxide, a flexible, non-conjugated between two aryl groups, and bent molecule, have been used to synthesize complexes with some carboxylic acid containing compounds. The study shows that although the occurrence of pyridyl⋯acid synthon is more than the corresponding pyridyl N-oxide⋯acid synthon, based on the distance criterion and energy calculation, the pyridyl N-oxide⋯acid synthon is slightly stronger than the pyridyl⋯acid synthon. Solubility studies also show that the pyridyl N-oxide compound may be a better choice as a coformer than the corresponding pyridyl derivative to increase the solubility of carboxylic acid containing compounds.

Network and guest dependent thermal stability and thermal expansion in a trigonal host

AbstractThermal stability and thermal expansion of bromo trimer synthon mediated hexagonal inclusion compounds of 2,4,6-tris(4-bromophenoxy)-1,3,5-triazine (BrPOT) with dichloromethane (DCM), tetrahydrofuran (THF) and hexamethyl benzene (HMB) and also the guest-free form of BrPOT are reported. Each of these three guests produced two concomitant inclusion compounds with BrPOT. The thermal stability of the solvate lattice increases with decreasing cavity size. The channel network of the DCM inclusion compound is stable only for a few seconds at room temperature outside the mother liquor, whereas the cage network of the DCM solvate is stable for months under similar conditions. Thermal expansions of the lattices depend upon the network, guest content as well as the type of guest molecules. The guest-free form exhibits the least thermal expansion in this series of systems. Graphical AbstractThermal stability and thermal expansion of hexagonal inclusion compounds of 2,4,6-tris(4-bromophenoxy)-1,3,5-triazine with dichloro- methane, tetrahydrofuran and hexamethyl benzene and also the guest-free form are reported.

Inclusion of a chiral guest in a centrosymmetric organic host lattice

Crystal structures of the racemic 2-methyl-1-butanol and (S)-(−)-2-methyl-1-butanol solvates of the complex of 2,4,6-triethyl-1,3,5-benzenetricarboxylic acid·4,4′-bipyridine and the guest free form of this complex are reported. The solvates are isoskeletal and the host networks are centrosymmetric. On heating, the solvates are converted to the guest free form which shows similar two-dimensional hydrogen bonding topologies, with the two-dimensional layers interpenetrated.

Hexagonal packing of cis,cis-cyclohexane-1,3,5-tricarboxamide.

The title compound, C(9)H(15)N(3)O(3), which has crystallographically imposed threefold symmetry, crystallizes as a hexagonal columnar structure. The crystal structure is stabilized by a less common amide-amide synthon, where one amide group is hydrogen bonded to four others. The amide groups form cyclic amide-amide hexamers via N-H...O hydrogen bonds.