Energetics Of Molecular Complexes

Abstract

In general A or D may7 be molecules, molecule-ions, or atom-ions, but with the restriction that they7 are both in their totally symmetric ground states. With these restrictions the principal contributing term in the wave function of the ground state of the complex, <k.v, will usually be that in W. 4>0 itself is the wave function corresponding to a structure for the complex in which the binding of the two components is effected by classical intermolecular forces such as dipoledipole, ion-dipole, dipole-induced dipole interactions, etc., by7 hydrogen bonding, or by perturbation effects of higher order such as London forces. 0 is denoted the no-bond wave function. , the dative-bond wave function, corresponds to a structure of the complex in which an electron has transferred from the donor to the acceptor, and in which, besides all the forces listed above as operative in the structure corresponding to , there may also be weak chemical binding between the odd electrons now situated on the two components of the complex. If A and D are both neutral species, ion-ion attractive forces may account for a large part of the binding energy of the dative structure.If the donor is a weak base and the acceptor a weak acid, then frequently a third term, representing electron transfer from the acceptor to the donor, may

Charge-transfer complexes of conjugated polymers as intermediates in charge photogeneration for organic photovoltaics

“…Moreover, earlier studies did not find any signatures of CTC in blends of conjugated polymers with such a strong electronic acceptor as TCNQ and its derivatives [23]. Following the Mulliken's model [24], we have suggested that the overlap of the corresponding frontier molecular orbitals (donor's HOMO and acceptor's LUMO) is an important factor for CTC formation [11,25]. Therefore, elongated acceptors with a better match to the extended molecular orbitals of the conjugated chain are more beneficial for higher CTC absorption.…”

“…2). Such behavior can be explained in the frame of Mulliken's model [24]. The efficiency of recombination is proportional to the overlap between the wave functions of ground and charge-separated states.…”

Thermochemistry of some π-π charge transfer complexes formed between methylbenzene donors and π-electron acceptors

“…pyromellitic dianhydride (PMDA), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and 2,3-dicyano-pbenzoquinone (DCNQ). The experimental values of the transition energies, hvcr, [11,12] are used to evaluate some ofthe energy parameters, employing the model of Sonnesa and Daisey [13], and use is then made of these parameters to estimate the values of All: for the re-n* ground state complexes formed in the above systems via the empirical relation reported earlier from our laboratory" It is quite evident from Tables 1-3 that the whole set of theoretical data on AH: fall well within the experimental range of 4-17 kJ/mole for n-re* interactions reported in the literature [1]. However, the reliability of the theoretical AH: data could not be tested due to the non-availability of experimental data on these systems in the literature.…”

“…Here theoretical relations, though empirical in nature, should be competitive and may frequently provide better results. For those complexes for which there are no experimental data, theoretical AHf should replace the speculative guesswork often presented in the literature, especially for n-rr* CT complexes, where the magnitude of AHy is of the order of 4-17 kJ/mol [1] and hence the uncertainty in the experimental data is higher. Therefore, as a continuation of our studies on the thermochemistry of molecular complexes [2][3][4][5][6][7][8][9][10] in relation to AHr, we have examined the rr-n* CT complexes formed between methylbenzene donors and three acceptors, viz.…”

Energetics of n-π* and π-π* charge-transfer complexes formed between amine donors and chloranil as π-electron acceptor

“…Here, theoretical relations, though empirical in nature, should be competitive and may frequently provide better results. For those complexes for which there are no experimental data, theoretical AH should replace the speculative guesswork often presented in the literature [21]. In view of this, as a continuation of our studies on the energetics of molecular complexes in relation to AH [22], we have now extended the work to n-~* and ~-z~* CT complexes formed in the pyridine-chloranil and aniline-ehloranil systems.…”