The crystal structure and polymorphism of the well-known aminoazobenzene, N,N-dimethyl-4-aminoazobenzene (DAB) are studied; a second polymorph of DAB reported and the relationship between the two polymorphs studied using differential scanning calorimetry and by evaluating their lattice energies and absorption spectra. Without significantly strong intermolecular interactions present in the two forms of DAB, a balance between conformational strain and a cumulative π-orbital overlapping effect results in the existence of the enantiotropically related polymorphs and their alternative packing arrangements. The UV/vis spectra of the two polymorphs are different, thus illustrating the significance of small structural changes on the colour of a material, which could behave differently under particular sensing conditions. DAB has been used primarily as an acid/base indicator solution and a dye molecule and the implications of the polymorphic relationships established here are discussed with respect to the range of applications this molecule finds as a sensor and for its incorporation into various functional films and devices.
Bibliographical noteFunding Information:
This work was funded by a Leverhulme Trust Visiting Fellowship (to DLC), the EPSRC (grants EP/K004956/1 & EP/I033459/1) as well as a South African National Research Foundation Fellowship (NRF RCA to DLC). The computational work was facilitated by access to the UK National Supercomputer, ARCHER (EPSRC Grant EP/L000202) and XSEDE (NSF Grant ACI-1053575).
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics