Thiophene HOMO-LUMO energies

The range of the phototoxic region along a HOMO-LUMO energy gap axis for thiophene derivatives (within the PM3 Hamiltonian) coincides almost exactly with... 

It has been reported that the direct substitution of the benzene ring of ben-zothiophene in such compounds can be used as a tool for modification of electronic and photophysical properties of Tt-conjugated materials. In particular, the substituent effect on HOMO/LUMO energies, ionization potentials, electron affinities, and reorganization energies have been described for 4,6-di(thiophen-2-yl)pyrimidine derivatives (Scheme 36(b) 2014CTC(1031)76). 

In poly[2,5-bis(3,4-ethylene-dioxy-2-thienyl)pyridine], a copolymer of thiophene and pyridine in a 2 1 ratio, the effective HOMO and LUMO energy levels of the ir-system are controlled in such a way that both p-doped and n-doped states are accessible (Scheme 9) [43]. The thin fdms display multicolor... 

Electronic states of the fused-silole-thiophene derivatives have been obtained by ab initio MO calculations on model compounds at the level of RHF/6-31G. Relative HOMO and LUMO energy levels derived from the MO calculations are given in Table 18 <2004OM5622>. 

Theoretical ionization energies are in good agreement with the experimental values. For all the molecules, the HOMO-LUMO gap is larger for the most stable isomers. This confirms previous results that claim that the stability of aromatic hydrocarbons depends on the HOMO-LUMO gap. The principle of maximum hardness establishes that the system would be more stable if the global hardness, related to the HOMO-LUMO gap, is a maximum. As shown in Table 61, the HOMO-LUMO gap correlates well with the expected stability of these molecules and the energy difference between the HOMO and HOMO-1 for benzo[3]thiophene is smaller than for benzo[c]thiophene (Figure 27). Therefore, it is possible to use hardness as a criterion of stability. 

Table 61 HOMO-LUMO gap (Ah l) and HOMO-[HOMO-1] energy difference (Ah h-) in eV, for benzo[fa]thiophene and benzo[c]thiophene. Ali caicuiations with Perdew-Wang 1991 <1995Mi2>...

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