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

Abstract

This document is the Accepted Manuscript version of the following article: Jesus Calvo-Castro, et al, ???Impact of substituent effects on the Raman spectra of structurally related??N-substituted diketopyrrolopyrroles???, Vibrational Spectroscopy, Vol. 83, pp. 8-16, March 2016. Under embargo. Embargo end date: 22 December 2017. The Version of Record is available online at doi:https://doi.org/10.1016/j.vibspec.2015.12.004. Published by Elsevier Copyright ?? 2015 Elsevier B.V. All rights reserved.Control over vibrational frequency modes is important in optimising the performance and behaviour of conjugated organic materials employed as charge transfer mediators and optical components in optoelectronic devices. Raman spectroscopy represents a powerful technique that can be employed to determine the structural implications of molecular substitution on photophysical properties in such conjugated organic environments. Herein, we report for the first time, the optimised geometries for a series of eight systematically varied N-substituted diketopyrrolopyrroles as well as their experimental and computed Raman spectra, with special emphasis placed upon their spectral band assignments. Clear out-of-plane structural re-arrangements, including pyramidalisation of the lactam nitrogens arising from intramolecular H-bonding interactions were observed upon N-substitution in the reported systems, leading to significant vibrational frequency shifts for ??(Nsingle bondC) and ??(Cdouble bond; length as m-dashO) modes. In addition, mode scaling factors were determined and found to be comparable with those reported previously, employed using the same density functional. The following study addresses the implications of structural variation on the progression of those intense Raman modes which play a key role in tuning the photophysical properties of N-substituted diketopyrrolopyrrole systems and as such should be of broad interest to those developing functional materials based upon this molecular moti

Comparative study of the hydrogen bonding interactions between ester-functionalized/non-functionalized imidazolium-based ionic liquids and DMSO

“…39 The M06-2X/ 6-311++G** method is usually used to investigate weak interactions. [40][41][42][43][44] In this work, the M06-2X/6-311++G** method was used to optimize the geometric structure, vibration frequency and energy of ions/ion pairs/ion clusters, co-solvents and their complexes. The optimized geometries were local minima without virtual frequencies.…”

Fluorine Directed Two-Dimensional Cruciform π–π Stacking in Diketopyrrolopyrroles

“…We are engaged in the rational design and systematic engineering of crystalline and thin film architectures based upon N-substituted DPPs − and have recently demonstrated in a number of systems that small structural variations can systematically influence and control the packing motifs via manipulation of their single crystal intermolecular interactions. − We are specifically interested in the dramatic changes observed to intermonomer displacements in crystal derived π–π stacking dimer pairs in these systems, which are reported to play a crucial role in determining the charge transfer properties of organic semiconductors. − ,− We have shown that N-benzylation is an effective strategy in the molecular design of DPPs, with N-benzyl substituted single crystal examples characterized by close alignment along their short molecular axis with the emergence of slipped cofacial 1-dimensional π–π stacks − unlike their pigment and alkylated counterparts. − This close intermonomer alignment along the short molecular axis in N-benzyl DPP architectures is associated with larger computed intermolecular interactions which are desirable for the enhancement of π–π stacking thermal integrity and to furthermore maximize wave function overlap, which is critical in optimizing hole and electron transfer behavior.…”

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

“…5,8,9 Diketopyrrolopyrrole (DPP) based materials are exciting charge transfer mediators, with high mobilities reported in organic field effect transistors (OFETs). [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 pioneered the application of Truhlar's 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.…”

“…[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 pioneered the application of Truhlar's 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-the-art quantum mechanical calculations describing non-covalent interactions through its inclusion of important medium distant London dispersion forces.…”