Crystal Engineering of Hand-Twisted Helical Crystals

Abstract

A strategy is outlined for the design of hand-twisted helical crystals. The starting point in the exercise is the one-dimensional (1D) plastic crystal, 1,4-dibromobenzene, which is then changed to a 1D elastic crystal, exemplified by 4-bromophenyl 4'-chlorobenzoate, by introduction of a molecular synthon -O-CO- in lieu of the supramolecular synthon Br···Br in the precursor. The 1D elastic crystals are next modified to two-dimensional (2D) elastic crystals, of the type 4-bromophenyl 4'-nitrobenzoate where the halogen bonding and C-H···O hydrogen bonding are well-matched. Finally, varying the interaction strengths in these 2D elastic crystals gives plastic crystals with two pairs of bendable faces but without slip planes. Typical examples are 4-chlorophenyl and 4-bromophenyl 4'-nitrobenzoate. This type of 2D plasticity represents a new type of bendable crystals in which plastic behavior is seen with a fair degree of isotropic character in the crystal packing. The presence of two sets of bendable faces, generally orthogonal to each other, allows for the possibility of hand-twisting of the crystals to give grossly helical morphologies. Accordingly, we propose the name hand-twisted helical crystals for these substances.

Indentation Plasticity and Fracture Studies of Organic Crystals

“…The modulation of mechanical properties of a molecular solid by modifying intermolecular interactions has been achieved by some researchers [64,92,93]. Therefore, future aims should work towards engineering functional molecular solids with desired physical and chemical properties with the knowledge gained from the subject of crystal engineering and structure-mechanical property correlations.…”

“…These 2-D elastic crystals were then transformed into 2-D plastic crystals (4-chlorophenyl and 4-bromophenyl 4'-nitrobenzoate) with two pairs of bendable faces without slip planes by varying interaction strengths. The presence of two pairs of bendable faces which are orthogonal to each other allowed the crystals to hand twist in a helical shape [64]. This shows that prior knowledge of the structure-mechanical properties of molecular crystals such as plastic and elastic mechanical deformation are necessary to engineer the molecular crystals with desired properties.…”

“…Recently, Sajesh et al [63] examined the plastic bending mechanism in Dimythl Sulfone (DMS) using a new bending model that provides quantitative rationalization based on differential binding and the stacking of molecular layers in orthogonal directions. Saha and Desiraju [64] reported a method to design hand-twisted helical crystals from plastic crystals using crystal engineering techniques (see Figure 5). The procedure was started with a 1-D plastic crystal (1,4-dibromobenzene), which was then converted to a 1-D elastic crystal (4-bromophenyl 4'-chlorobenzoate).…”

“…This shows that prior knowledge of the structure-mechanical properties of molecular crystals such as plastic and elastic mechanical deformation are necessary to engineer the molecular crystals with desired properties. Saha and Desiraju [64] reported a method to design hand-twisted helical crystals from plastic crystals using crystal engineering techniques (see Figure 5). The procedure was started with a 1-D plastic crystal (1,4-dibromobenzene), which was then converted to a 1-D elastic crystal (4-bromophenyl 4'-chlorobenzoate).…”

Synthesis and crystal structure of N,N-dimethylformamide solvate of thiocyanuric acid

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Abstract Considerable attention has been paid recently to crystal engineering; which involves the design and preparation of new crystalline molecular solids with desired properties [1][2][3][4]. Crystalline materials with specific properties find applications in petrochemical industry for separation and purification.

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