A Computational Study on the Stacking Interaction in Quinhydrone

Abstract

The stability and electron density topology of quinhydrone complex was studied using multiple computational levels, including MPW1B95 Truhlar's density functional. The QTAIM analysis demonstrates that an electron population transfer from hydroquinone to quinone monomer accompanies the complex formation. The variations undergone by atomic populations indicate that the electron transfer through HOMO LUMO overlap is combined with a reorganization of the electron density within each monomer. Variations of two- and six-center delocalization indices show a small reduction of electron delocalization in the hydroquinone ring upon complex formation.

Quinone–hydroquinone complexes as model components of humic acids: Theoretical studies of their structure, stability and Visible–UV spectra

“…This is the trend expected on the basis of Sinnokrot and Sherrill (2006). Gonzalez Moa et al (2007) indicate the MPW1B95 results are in good agreement with the experimental values. However, this is not necessarily true, since no geometry optimization was done in Gonzalez Moa -an experimental geometry was used.…”

“…The HOMO of the donor H 2 Q and the LUMO of the acceptor Q (not shown) are quite similar to those shown in Fig. 2 of Gonzalez Moa et al (2007). As shown in the last row of Table 4, the difference of the donor HOMO eigenvalue and the acceptor LUMO eigenvalue is 1.84 eV, quite close to the calculated TD B3LYP transition energy of 1.97 eV for H 2 Q/Q.…”

“…A truly accurate method such as large basis set CCSD or CCSD(T) (Scuseria and Schaefer, 1988;Helgaker et al, 1997) is not presently feasible for such systems. Many studies on similar systems have used medium or large basis set MP2 (Pople et al, 1976) methods, which seem to generally give good geometries but overestimate binding energies (Sinnokrot and Sherrill, 2006;Gonzalez Moa et al, 2007). There are also density functional methods employing new potentials, such as MPW1B95 (Zhao and Truhlar, 2006) which have shown promise in treating interactions between aromatic molecules.…”

Computational Study on the Stacking Interaction in Catechol Complexes

“…In contrast, we have found a negative value for this quantity ( Table 4) that can be explained assuming HOMO-LUMO transferences are accompanied by F(r) reorganization among the atoms of each monomer, as was previously proposed for quinhidrone complex. 9 C-H/π Dimer (D 2 ). As above indicated this dimer is less stable than D 1 both if stability is measured through ∆ c E or ∆ b E values; the latter referred either to crystal or optimized geometries (Table 2).…”

The use of a molecular balance derived from 5,5′-bipyrazole to calculate π−π stacking interactions

“…Mosquera et al have reported similar interactions for stacking of quinhydrone. 16 Encouraged by these results, we decided to explore other possibilities replacing the phenyl rings of 3 by other aromatic groups (neutral: 4-8) and (charged: 9). We have removed the methyl groups of compound 3 (3 0 without methyl groups) since they are unnecessary.…”