Decomposition analyses of the intermolecular interaction energies in two ππ stacking complexes: Quinhydrone and N,N,N′, N′‐tetramethyl‐P‐diaminobenzene‐chloranil complex

Abstract

Although there is a similarity in the orbital interaction scheme between quinhydrone and N,N,N′,N′‐tetramethyl‐p‐diaminobenzene‐chloranil complex, the stacking conformations are different from each other. The former prefers the half‐stacked conformation, whereas the latter prefers the completely stacked conformation. We have done ab initio molecular orbital calculations and decomposition analyses of the intermolecular interaction energies to clarify the origin of the different stacking conformations. It was concluded that the main origin is the difference in the steric part of the interaction energies. © 1994 by John Wiley & Sons, Inc.

Unraveling the interplay of different contributions to the stability of the quinhydrone dimer

“…3, which allows also for a comparison with previous literature ndings. 46,54 All results are reported in Table 3, where it is apparent that both MP2/mod and M06-2X (with both basis sets) well agree with the computed CCSD(T)/CBS binding energy: the error of the WF based method is only of $0.2 kcal mol À1 , whereas the DFT approach overestimates the reference data by less than 0.8 kcal mol À1 . Conversely, the literature data tend to severely underestimate the stability of the dimer by about 3 kcal mol À1 , making the use of both standard basis set with MP2 and the MPW1B95 functional rather questionable.…”

“…1) whose ubiquitous presence in many aspects of organic matter has motivated an extensive number of experimental and theoretical studies. [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] Quinhydrone is made by two units, namely p-benzoquinone and hydroquinone and it is known from a century and an half, being rst discovered in 1844 by Wöhler. 41 It can be prepared by a 1 : 1 mixture of the two components or just by partial reduction of p-benzoquinone in ethyl alcohol.…”

“…51,55 Despite its importance, relatively few computational studies have been reported in literature on the structural and spectral characterization of quinhydrone. The rst reliable calculations were performed, to the best of our knowledge, in 1994 by Kurita, 46 where single point calculations at MP2/6-31G* level, using Counterpoise (CP) correction, 59 were performed on a geometry reconstructed from experimental (X-ray) data. 43,44 The authors concluded that electron correlation effects are essential to stabilize quinhydrone and that the relative orientation of the stacked complex is determined by the interplay of many interaction terms as steric repulsion, CT interaction energy, dispersion and rst order electrostatics.…”

“…More recently, 54 the stability and electron density topology of quinhydrone was studied using computational methods of various level of accuracy. The authors aimed to rene Kurita's et al calculations, 46 taking into account the role of H-bond, which was found to be relevant by some experiments. 49 Furthermore, the authors nd, through a QTAIM analysis, a small electron transfer of 0.046 a.u., from hydroquinone to p-benzoquinone.…”

Orbital-based insights into parallel-displaced and twisted conformations in π–π interactions

“…18 For p-stacked DNA bases, the dependence on the twist angle as well as parallel displacement, 19 is believed to arise from electrostatics and the dipole-dipole attraction. 19,20 Despite being invoked in donor-acceptor p-p interactions, 7,[21][22][23][24][25] orbital interactions are discussed abstractly, through energy decompositions 26 or as perturbations of the p cloud 13 and have been largely discounted as an explanation of p-stacking and other noncovalent interactions. 17,27 As a result, an in-depth molecular orbital (MO) analysis of p-stacking interactions has yet to be explored.…”