Combined ab initio and density functional study on polaron to bipolaron transitions in oligophenyls and oligothiophenes

Abstract

Articles you may be interested inLow-lying absorption and emission spectra of pyrene, 1,6-dithiapyrene, and tetrathiafulvalene: A comparison between ab initio and time-dependent density functional methods Model ab initio study of charge carrier solvation and large polaron formation on conjugated carbon chains Accurate ab initio density fitting for multiconfigurational self-consistent field methodsThe water exchange process of tetraaquaplatinum(II): Density-functional theory and ab initio computational study Ab initio self-consistent-field ͑SCF͒, two-configuration SCF ͑TCSCF͒, and density functional theory ͑DFT͒ calculations on the charge-transfer complexes of doubly Li/Cl-doped oligothiophenes and oligo͑p-phenyls͒ and on respective charged systems without counterions have been carried out in order to study polaron to bipolaron transitions. Oligomer chains up to octamers and the ring structures cyclo-dodecathiophene and cyclo-dodeca͑p-phenyl͒ have been investigated. Special attention is paid to the open-shell biradical character of two isolated polaronic defects. It is found that the TCSCF and the spin-unrestricted DFT methods can be successfully applied. A bipolaron structure is obtained when the doping atoms are located on neighboring rings and when there is one undoped ring separating the two doped ones. If there are two or more undoped rings in between a two-polaron configuration ͑biradical͒ is found. The bipolaron system is calculated to be more stable than the two-polaron case when counterions are taken into account. The stabilities are reversed if the bare, doubly-charged systems are considered. A theoretical estimate for the barrier height of the polaron to bipolaron transition is given using model reaction coordinates.

Redox States of Long Oligothiophenes: Two Polarons on a Single Chain

“…We might actually expect the relative stability of one bipolaron versus two polarons to result from a fine balance depending intimately on the experimental conditions, such as solvent and type of counterions. [64] Experimental Section…”

Interaction of singlet excitons with polarons in wide band-gap organic semiconductors: A quantitative study

“…Since quantum chemical calculations for oligophenyls 44 show that polarons which are separated by a distance of one phenyl ring can already by treated as uncorrelated, we assume that the magnetic resonance enhancement of both nongeminate and geminate recombination works in a similar way. In order to recombine, the polarons must form a correlated pair, with sufficient spin polarization so that at the field for resonance one can sufficiently enhance the recombination of the pairs and, hence, decrease the total polaron population.…”

Electronic structure of Li-intercalated oligopyridines: A comparative study by photoelectron spectroscopy

“…The gradual manner in which the Fermi energy shifts as a function of intercalation level also provides some evidence of a transition from a polaronic to a bipolaronic state. 13,44,45 Lischka and co-workers 19,20,46,47 have theoretically analyzed the position of intercalated lithium atoms with respect to the molecules within isolated Li-BP complexes. According to their calculations, a single lithium atom interacts through a cation-binding configuration, where the Li counterion is approximately equidistant from the carbon atoms in one of the BP rings and positioned almost directly above the center of that ring.…”