DescriptionWe have prepared and determined the crystal structures of a series of N-benzyl substituted diphenyldiketopyrrolopyrroles (DPPs). In all cases the crystal structures indicate the presence of 1-D pi-pi stacking motifs exhibiting varying degrees of co-facial slip. Systematic substitution at the para position of the phenyl substituent (X = H, Cl; two polymorphs, Br, butoxyphenyl) leads to systematic variation in pi-pi co-facial slip such that very large variation in computed charge transfer integrals (th/e) are observed for centrosymmetric pi-pi co-facial dimers extracted from the crystal(s), while at the same time, little variation in computed hole and electron re-organisation energies (for single molecules) are observed across the series. The variation in the amplitude of te/h with the extent of pi-pi co-facial slip can be rationalised based on model DPP dimer, long molecular axis ‘fly-by’ calculations (employing M06-2X/6-31G(d) and M06-2X/6-311G(d) DFT methods). We see examples of te > th, th > te, te = th where some th/e values approach and may exceed those computed for rubrene. In short, computational results associated with electronic coupling between the pi-pi stacked dimer pairs and (single molecule) structural reorganisation energies suggest charge transfer along this series of crystalline pi-pi stacks may exhibit the full gamut of band-like to thermally driven charge transport regimes.
|Period||12 May 2015|
|Event title||European Materials Research Society Spring Conference 2015: Symposium Q - Organic semiconducting single crystals: from fundamentals to advanced devices|
|Degree of Recognition||International|