Elsevier, Journal of Molecular Structure, (1078), p. 74-82
DOI: 10.1016/j.molstruc.2014.04.088
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The novel compound Z-2-phenyl-3-(4-(pyridin-2-yl)phenyl)acrylonitrile (PPyPAN) was synthesized from the condensation reaction between phenylacetonitrile and 4-(pyridin-2-yl)benzaldehyde. This compound crystallizes in two forms: polymorph I (triclinic, P - 1, Z' = 2) and polymorph II (orthorhombic, Pbc2(1), Z' = 2). The molecular structures and optical properties of the two polymorphs have been characterized via H-1 NMR, El, FTIR, UV-Vis spectroscopy, DSC, single-crystal and XRPD. The molecular structure, packing properties, and intermolecular interactions were examined for both polymorphs of PPyPAN in order to interpret the emission properties. A subtle change in the molecular conformation (e.g., a rotation around single C-C bonds) found for both polymorph plays an important role in their solid-state properties. The structure and optical properties of the new structures were well characterized and showed unique features for both polymorphic phases. For phase I, we observed an excitation spectrum with an lambda(ex) at 325-346 nm, which is the maximum excitation or absorption wavelength for the lowest S-0 -> S-1 transition, which is characteristic to the pi-pi* transition, and an emission spectrum with an lambda(max)(em) at 454 nm. For phase II, the excitation spectrum showed an lambda(max)(ex) at 325 nm, whereas the lambda(max)(em) showed a red-shift to 492 nm.