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Updated: Jun 29, 2026

Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
Theoretical analysis of the intermolecular interaction effects on the excitation energy of organic pigments: solid
Hiroo Fukunaga1, Dmitri G Fedorov, Mahito Chiba
1Imaging Technology Center, Research & Development Management Headquarters, FUJIFILM Corporation, FFTP M0-6F, 1250, Takematsu, Minamiashigara-shi, Kanagawa 250-0111, Japan. hiroo_fukunaga@fujifilm.co.jp
Abstract:
Quinacridones (QAs) are organic hydrogen-bonded pigments, which are yellow in solution and become reddish to violet in solid phase depending on the crystal structure. We have carried out regular and fragment molecular orbital (FMO) based time-dependent density functional theory (TDDFT) calculations of the alpha (I), beta, and gamma crystalline phases of QA to examine the origin of the spectral shift in the solid phase. On the basis of the TDDFT calculations, we have found that the spectral shift from gas to solid phase in QA is dominated by the interplay of the structural deformation, electrostatic potential (crystal field), and intermolecular interactions, and each contribution is of the same order of magnitude. The spectral shift induced by the structural deformation is mainly caused by the stretch of the CO bond. The individual intermolecular interactions contribute to bathochromic and hypsochromic shifts depending on the spatial orientation, and their sums result in the bathochromic shift overall.
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