DLPNO-CCSD(T) scaled methods for the accurate treatment of large supramolecular complexes

Abstract

In this work, we present scaled variants of the DLPNO-CCSD(T) method, dubbed as (LS)DLPNO-CCSD(T) and (NS)DLPNO-CCSD(T), to obtain accurate interaction energies in supramolecular complexes governed by noncovalent interactions. The novel scaled schemes are based on the linear combination of the DLPNO-CCSD(T) correlation energies calculated with the standard (LoosePNO and NormalPNO) and modified (Loose2PNO and Normal2PNO) DLPNO-CCSD(T) accuracy levels. The scaled DLPNO-CCSD(T) variants provide nearly TightPNO accuracy, which is essential for the quantification of weak noncovalent interactions, with a noticeable saving in computational cost. Importantly, the accuracy of the proposed schemes is preserved irrespective of the nature and strength of the supramolecular interaction. The (LS)DLPNO-CCSD(T) and (NS)DLPNO-CCSD(T) protocols have been used to study in depth the role of the CH-π versus π-π interactions in the supramolecular complex formed by the electron-donor truxene-tetrathiafulvalene (truxTTF) and the electron-acceptor hemifullerene (C H ). (NS)DLPNO-CCSD(T)/CBS calculations clearly reveal the higher stability of staggered (dominated by CH-π interactions) versus bowl-in-bowl (dominated by π-π interactions) arrangements in the truxTTF•C H heterodimer. Hemifullerene and similar carbon-based buckybowls are therefore expected to self-assemble with donor compounds in a richer way other than the typical concave-convex π-π arrangement found in fullerene-based aggregates. © 2017 Wiley Periodicals, Inc.

Understanding non-covalent interactions in larger molecular complexes from first principles

“…Calbo et al 102 demonstrated in a recent study that supramolecular complexes require tight PNO settings, in order to obtain converged results with DLPNO-CCSD(T). It was shown that normal PNO settings result in DLPNO-CCSD(T) overestimating π − π and CH- π dispersion interactions 102 . In some cases, however, an ad hoc scaling factor is applied to normal PNO obtained results, in order to estimate the converged result.…”

“…This basis set dependence makes the computation of intermolecular interactions particularly challenging for large systems. Some previous studies 102,127 have used scaling factors to circumvent the use of a sufficiently large basis set. Applying a basis set scaling factor for larger systems introduces an uncontrolled level of uncertainty in the final result.…”

Quantum-Chemical Insights into the Self-Assembly of Carbon-Based Supramolecular Complexes

“…From a theoretical point of view, counterintuitive staggered structures ( A3 and A4 ) were suggested as the most stable arrangements for the truxTTF•C 30 H 12 supramolecular heterodimer. Remarkably, the supramolecular prediction at the DFT-D3 level was recently confirmed by high-level theoretical calculations at the DLPNO-CCSD(T) level of accuracy [ 109 ], and by another experimental–theoretical study conducted by us on related buckybowl systems ( Section 3.2.2 ) [ 19 ]. The theoretical study of the truxTTF•C 30 H 12 complex therefore represents a good example where quantum-chemical calculations were decisive to provide a deep insight into the supramolecular organization of truxTTF•C 30 H 12 , which turned out to be strikingly different compared to that found for its truxTTF•C 60 homologue.…”

Bending Carbon Nanoforms for Supramolecular Recognition: A Topological Study on Hemifullerene-Based Aggregates

“…The energetic order predicted at the DFT level for structures 3-6 was confirmed by high-level DLPNO-CCSD(T) theoretical calculations. 27 In order to understand the origin of the forces driving the self-assembly between two hemifullerenes, and between hemifullerene and the donor truxTTF moiety, we analyzed the reduced density gradient (NCI index) using the NCIPLOT software. Figure 2a displays the 3D plots of NCI surface for the two most stable homodimers of benzene (parallel displaced or PD, and Tshape or T) and hemifullerene (bowl-in-bowl 1 and staggered 2).…”

“…These trends are in good accord with the values computed at the revPBE0-D3/cc-pVTZ level, 26 and with those recently reported using high-level DLPNO-CCSD(T) calculations. 27 In order to have a workable (low computational cost) approach to comprehensively analyze the hemifullerene-based aggregates and to study the effect of the molecular curvature in the assembly (see below), we compared the interaction energies calculated using the 6-31G** basis set, both uncorrected and counterpoise (CP)-corrected, with the nearly basis set superposition error (BSSE)-free results obtained with the Dunning's cc-pVTZ basis set (Table 1). Uncorrected interaction energies using the 6-31G** basis set are significantly overestimated compared to the cc-pVTZ values for the series of hemifullerene-based dimers 1-6.…”