Thermomechanical effect in molecular crystals: the role of halogen-bonding interactions
| Title | Thermomechanical effect in molecular crystals: the role of halogen-bonding interactions |
| Publication Type | Journal Article |
| Year of Publication | 2017 |
| Authors | Mittapalli, S, D. Perumalla, S, Nanubolu, JBabu, Nangia, A |
| Journal | IUCRJ |
| Volume | 4 |
| Issue | 6 |
| Pagination | 812-823 |
| Date Published | NOV |
| Type of Article | Article |
| Abstract | The design and synthesis of mechanically responsive materials is interesting because they are potential candidates to convert thermal energy into mechanical work. Reported in this paper are thermosalient effects in a series of halogen derivatives of salinazids. The chloro derivative, with higher electronegativity and a weaker inter-halogen bond strength (Cl center dot center dot center dot Cl) exhibits an excellent thermal response, whereas the response is weaker in the iodo derivative with stronger I center dot center dot center dot I halogen bonding. 3,5-Dichlorosalinazid (Compound-A) exists in three polymorphic forms, two room-temperature polymorphs (Forms I and II) and one high-temperature modification (Form III). The transformation of Form I to Form III upon heating at 328-333 K is a reversible thermosalient transition, whereas the transformation of Form II to Form III is irreversible and nonthermosalient. 3,5-Dibromo- (Compound-B) and 3-bromo-5-chloro(Compound-C) salinazid are both dimorphic: the Form I to Form II transition in Compound-B is irreversible, whereas Compound-C shows a reversible thermosalient effect (362-365 K). In the case of 3,5-diiodosalinazid (CompoundD) and 3,5-difluorosalinazid (Compound-E), no phase transitions or thermal effects were observed. The thermosalient behaviour of these halosalinazid molecular crystals is understood from the anisotropy in the cell parameters (an increase in the a axis and a decrease in the b and c axes upon heating) and the sudden release of accumulated strain during the phase transition. The dihalogen salinazid derivatives (chlorine to iodine) show a decrease in thermal effects with an increase in halogen-bond strength. Interestingly, Compound-B shows solid-state photochromism in its polymorphs along with the thermosalient effect, wherein Form I is cyan and Form II is light orange. |
| DOI | 10.1107/S2052252517014658 |
| Type of Journal (Indian or Foreign) | Foreign |
| Impact Factor (IF) | 5.793 |
Divison category:
Physical and Materials Chemistry
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