Application of a Computational Systematic Search Strategy to Study Polymorphism in Phenazine and Perylene

Abstract

The materials phenazine and perylene have been previously reported to exhibit polymorphic behavior. Experimental evidence suggests that both molecules can exist in at least two polymorphic forms. In the case of phenazine, only one polymorph has a fully described crystal structure. In the case of perylene, two polymorphs have a reported structure, from single-crystal studies; however, one structure solution is of poor quality. This paper reports the results of a molecular modeling study and postulates crystal structures for the two polymorphs which lack a reliable experimental determination. Systematic searches of potential packing arrangements were conducted in the reported cells for both the solved and unsolved polymorphs of phenazine and perylene. A recently validated search method (Hammond, R. B.; Roberts, K. J.; Docherty, R.; Edmondson, M. J. Phys. Chem. B 1997, 101, 6532) was employed to rank packing arrangements by considering nonbonded atom−atom distances in combination with calculated lattice energies. The molecular packing arrangements were compared and contrasted using the packing energy breakdown routines within the program HABIT95 (Clydesdale, G.; Roberts, K. J.; Docherty, R. Quantum Chemistry Program Exchange 1996, 16, 1).

Polymerization of aniline under various concentrations of APS and HCl

“…3,10,38 On the other hand, the C:H atomic ratios are slightly larger than the theoretical ratios. For dedoped samples, the excess H atoms may come from the adsorption of H 2 O molecules, 39,40 whereas for doped samples, the source of additional H atoms may be due to the adsorption of HCl or H 2 SO 4 molecules (see Figure 1).…”

“…Figure 11 shows the XRD patterns of samples obtained from various cases. From the data of the a-phenazine structure (monoclinic, a¼7.1 Å , b¼5.1 Å , c¼12.8 Å , b¼102.31), 38 we calculated and assigned the distinguishable peaks to their corresponding planes as indicated in Figure 11a. Thus, samples obtained from case (A) are confirmed to be composed of phenazine segments with order stacking.…”

Tetraaminoperylenes: Their Efficient Synthesis and Physical Properties

“…This development was supplemented by the proposal of classification schemes for the arrangement of such polyaromatics in crystals. [25] The solid-state structures of a large number of biscarboximide perylene derivatives have been studied in order to investigate the correlation between molecular packing and color in pigments. [26] In most cases, stacked ™face-to-face∫ arrangements (separations of between 3.345 and 3.476 ä between the parallel oriented ring systems) of perylenes are found, provided that there are no bulky substituents preventing this.…”

Towards a Complete Description of a Polymorphic Crystal: The Example of Perylene

“…In the absence of a measured value for DH for perylene, we use the value of 12.8 kJ/ mol calculated by Hammond et al [8], and for DV our measured value of 2.8 ä . This is an upper bound on T c , and not necessarily the thermodynamic equilibrium temperature.…”

“…A room-temperature highpressure infrared study provided no evidence for a phase transition below 45 kbar [7]. A systematic computational search strategy has been used to study polymorphism in perylene [8] (and, also, in phenazine, where the XRD structures of both polymorphs (cf. [9a, b]) are in good agreement with the predictions, as they are for perylene).…”