Theoretical study on photophysical properties of novel bis(BF₂)‐2,2′‐bidipyrrins dyes: Effect of variation in monomer structure

Abstract

In this work, monomeric molecules (BODIPY) 4,4-difluoro-1,2,3,5,7-pentamethyl-6-ethyl-4-bora-3a,4a-diaza-s-indacene (1), 4,4-difluoro-1,7-dimethyl-2,3,6-terethyl-8-(4-tolyl)-4-bora-3a,4a-diaza-s-indacene (Ph1), dimeric monomers (bisBODIPY) 2, Ph2, and their packing systems were taken as calculation models to investigate the relationship between monomeric structures and spectral properties of packing systems. Their spectra and carrier transport properties were systemically investigated by density functional theory and time-dependent DFT methods. The results reveal that dimeric monomers bisBODIPY 2 and Ph2 show significantly bathochromic shift and exhibit a clear exciton splitting in the absorption spectrum compared with those of 1 and Ph1. Monomeric and dimeric molecules have different monomer conformations (nearly flat and corniform, respectively) and thus diverse packing styles. The intermolecular aggregation affects the excitation energy and oscillator strength of monomers 1 and Ph1 more than those of the corniform monomers 2 and Ph2. The unique corniform structure of molecules 2 and Ph2 can greatly reduce self-quenching effect induced by the formation of excimers. This means that suitable modification of molecular arrangement is an effective way to reduce self-quenching. From the calculation results for molecules Ph1 and 1, the aryl group at the 8-position of BODIPY core can hardly affect the optical properties. According to our calculations, BODIPY 1 is a better hole transporter than electron transporter with the internal reorganization energy for hole (k þ ) even lower than that of 4,4 0 -bis(phenyl-mtolylamino)biphenyl (TPD), a well-known holetransporting material. Molecules Ph1, BisBODIPYs 2, and Ph2 are promising candidate to be excellent ambipolar materials for electroluminescent devices, owing to their quite small and nearly identical reorganization energies for both carriers.

Ferrocene: An unrivaled electroactive building block for the design of push-pull dyes with near-infrared and infrared absorptions

“…Authors also demonstrated this unexpected elongation of the excited state lifetime to result from complex excited-state dynamics. Upon excitation, the initial excited state resulted in a charge separation state with a reorganization energy of 0.5 eV which is much greater than that reported for similar systems [70]. Following the initial charge separation, a rapid charge recombination occurring in the inverted Markus regime results in the formation of a triplet state lo cated either on the aza-BODIPY or the ferrocene unit.…”

Strong Electronic Coupling Dominates the Absorption and Fluorescence Spectra of Covalently Bound BisBODIPYs

“…For example, considering BODIPY-based triads, which are bound to each other using ethynyl-dibutoxyphenyl linkers, it was shown that energy transfer between the terminal BODIPYs occurs primarily by way of through-bond, that is, electron exchange, interactions. 11 Along the same line of thought, BisBODIPY derivatives were investigated using (timedependent) density functional theory (TDDFT), and they were found to have both a high charge-transfer rate and high photoluminiscence efficiency in the solid state, 12 which makes them excellent candidates for ambipolar materials for use in OLEDs for instance.…”