Torsional angle dependence and switching of inner sphere reorganisation energies for electron and hole transfer processes involving phenyl substituted diketopyrrolopyrroles; a density functional study

Abstract

angle dependence and switching of inner sphere reorganisation energies for electron and hole transfer processes involving phenyl substituted diketopyrrolopyrroles; a density functional study ', Dyes and Pigments, Vol. 113, pp. 609-617, February 2015 AbstractDetermination of inner sphere reorganisation energies is important in the development of organic charge mediating materials and electron transfer reactions. In this study, hole and electron inner sphere reorganisation energies, λ h and λ e respectively, have been computed for the first time for a series of structurally related diketopyrrolopyrrole (DPP) molecular motifs. Inner sphere reorganisation energies for self-exchange electron transfer reactions are calculated as being lower than those associated hole transfer processes in model planar phenyl and thiophenyl substituted DPP systems. It is found that λ e < λ h for all planar ring / DPP core structures examined. The effect on λ h/e of nonplanarity between phenyl substituents and DPP core is explored in detail. The relative ordering of λ h and λ e is dependent upon the torsional angle of phenyl rings and reverses at twist angles of greater than 60⁰ such that λ e > λ h .

Impact of substituent effects on the Raman spectra of structurally related N-substituted diketopyrrolopyrroles

“…In fact, we have recently reported that the optimised geometries of H 2 DPP are strictly non-planar for a series of hybrid density functionals, with the dihedral angle between the phenyl rings and the core found to increase with increasing amount of Hartree-Fock exchange in the functional. [23] In relation to the Raman spectrum, this results in degeneracy of the in-plane and outof-plane modes to a g . Similarly, the asymmetrical in-plane and out-of-plane modes are degenerated to a u .…”

“…[20,21] Along these lines, in centrosymmetric systems such as those investigated herein, the most intense Raman active modes are known to exert control over the vibronic progression in absorption and emission spectra, where the quantum spacing ℎ determines the spacing between the maxima of the different Gaussian peaks forming the progression, as well as determining the intramolecular reorganisational energies, allowing a mode-by-mode analysis where the total reorganisation energy is computed as the sum of the products of the frequency of the different vibrational modes weighted by the associated electron vibrational coupling or Huang-Rhys factors. [22,23] These denote the one dimensional displacement of the potential energy surfaces of the initial and final states involved in the transition with respect to the reaction coordinate. [22,24,25] As a consequence, rationalisation of the substitution effects on shifting the frequency of the most intense Raman active modes represents a very powerful tool in engineering future materials to match with desirable molecular properties.…”

Twist and shout: a surprising synergy between aryl and N-substituents defines the computed charge transport properties in a series of crystalline diketopyrrolopyrroles

“…60° a reversal of the inner-sphere reorganisation energies e h . 27 This characteristic behaviour is attributed to an out-of-plane rearrangement primarily associated to the C-C linker between the DPP core and the core phenyl rings. The structural re-arrangement was Please do not adjust margins…”

“…[10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] Our group are engaged in the rational design of crystalline and thin film DPP architectures [27][28][29][30][31][32][33] and have demonstrated in a number of phenyl core-substituted N-benzyl DPPs that small structural variations, particularly involving halogenation, can profoundly influence supramolecular packing via manipulation of single crystal intermolecular interactions. 28,29,31,32 We have T M06-2X density functional in the theoretical analysis of charge transfer integrals, reorganisation energies and interaction energetics in DPPs, [27][28][29][30][31][32][33] many of which are comparable or supersede those computed for the single crystal structures of state of the art organic semiconductors such as rubrene. 29 The M06-2X semilocal density functional has been shown to quantitatively agree with state-of-theart quantum mechanical calculations describing noncovalent interactions through its inclusion of important medium distant London dispersion forces.…”

Screening and design of high-performance indoline-based dyes for DSSCs

“…The reorganization energy can be divided into the intermolecular recombination energy and the intramolecular recombination energy. 46 The intermolecular recombination energy has no obvious effect on the charge transfer. 47 The energy of the neutral, cationic and anionic molecules can be used to calculate the reorganization energy.…”