Nonlocal van der Waals Approach Merged with Double-Hybrid Density Functionals: Toward the Accurate Treatment of Noncovalent Interactions

Noncovalent interactions drive the self-assembly of weakly interacting molecular systems to form supramolecular aggregates, which play a major role in nanotechnology and biochemistry. In this work, we present a thorough assessment of the performance of different double-hybrid density functionals (PBE0-DH-NL, revPBE0-DH-NL, B2PLYP-NL, and TPSS0-DH-NL), as well as their parent hybrid and (meta)­GGA functionals, in combination with the most modern version of the nonlocal (NL) van der Waals correction. It is shown that this nonlocal correction can be successfully coupled with double-hybrid density functionals thanks to the short-range attenuation parameter <i>b</i>, which has been optimized against reference interaction energies of benchmarking molecular complexes (S22 and S66 databases). Among all the double-hybrid functionals evaluated, revPBE0-DH-NL and B2PLYP-NL behave remarkably accurate with mean unsigned errors (MUE) as small as 0.20 kcal/mol for the training sets and in the 0.25–0.42 kcal/mol range for an independent database (NCCE31). They can be thus seen as appropriate functionals to use in a broad number of applications where noncovalent interactions play an important role. Overall, the nonlocal van der Waals approach combined with last-generation density functionals is confirmed as an accurate and affordable computational tool for the modeling of weakly bonded molecular systems

Accurate Treatment of Large Supramolecular Complexes by Double-Hybrid Density Functionals Coupled with Nonlocal van der Waals Corrections

In this work, we present a thorough assessment of the performance of some representative double-hybrid density functionals (revPBE0-DH-NL and B2PLYP-NL) as well as their parent hybrid and GGA counterparts, in combination with the most modern version of the nonlocal (NL) van der Waals correction to describe very large weakly interacting molecular systems dominated by noncovalent interactions. Prior to the assessment, an accurate and homogeneous set of reference interaction energies was computed for the supramolecular complexes constituting the L7 and S12L data sets by using the novel, precise, and efficient DLPNO-CCSD­(T) method at the complete basis set limit (CBS). The correction of the basis set superposition error and the inclusion of the deformation energies (for the S12L set) have been crucial for obtaining precise DLPNO-CCSD­(T)/CBS interaction energies. Among the density functionals evaluated, the double-hybrid revPBE0-DH-NL and B2PLYP-NL with the three-body dispersion correction provide remarkably accurate association energies very close to the chemical accuracy. Overall, the NL van der Waals approach combined with proper density functionals can be seen as an accurate and affordable computational tool for the modeling of large weakly bonded supramolecular systems

Light-Emitting Electrochemical Cells Using Cyanine Dyes as the Active Components

Light-emitting electrochemical cells (LECs) based on cyanine molecules were prepared. High photoluminescence quantum yields were obtained for host–guest films using two cyanine dyes, reaching 27%. Sandwiching these films in between two electrodes allows for very stable near-infrared emission with a maximum radiant flux of 1.7 W m^–2 at an external quantum efficiency of 0.44%

Tuning the Self-Assembly of Rectangular Amphiphilic Cruciforms

The self-assembly of a series of nonionic amphiphilic cruciforms based on the 1,2,4,5-tetrakis­(phenylethynyl)­benzene (TPEB) skeleton, in which the peripheral substituents have been modified to modulate the morphology of the supramolecular structures, is reported. The presence of linear paraffinic and hydrophilic chains in TPEBs <b>1</b> and <b>2</b> gives rise to two-dimensional structures of high aspect ratio. In contrast, the incorporation of dendronized hydrophilic chains results in the formation of twisted ribbons in amphiphile <b>3</b> and impedes the organized self-assembly of TPEB <b>4</b>. Theoretical calculations show that the self-assembly of these amphiphiles might be initiated with the formation of π-stacked dimeric units. Compound <b>2</b>, which self-assembles into different morphologies depending on the solvent, interacts by π-stacking and also by the interdigitation of the peripheral decyl tails to generate bidimensional supramolecular structures. The steric demand exerted by the dendronized polar wedges in <b>3</b> and <b>4</b> strongly conditions their supramolecular organization. This steric demand together with the interdigitation of the decyl chains results in the self-assembly of cruciform <b>3</b> into helical aggregates. However, the lack of the paraffinic chains in <b>4</b> impedes this helical organization, and the formation of amorphous material is visualized. The joint experimental and theoretical study presented herein provides relevant guidelines for the modulated self-assembly of nonionic amphiphilic molecules

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

Buckybowls have risen as appealing fullerene fragment derivatives. Their intrinsic curvature has been exploited in the generation of host–guest supramolecular assemblies, not only through concave–convex complementarity but also through less-known concave–concave staggered arrangements. Whereas the stabilization of bowl-in-bowl dispositions has been ascribed to efficient π–π forces together with favorable dipole–dipole interactions, a detailed analysis on the forces guiding the formation of the staggered arrangements is missing so far. Herein, we present a thorough theoretical characterization of bowl-in-bowl vs staggered hemifullerene-based homodimers and heterodimers with the electron-donor truxTTF molecule, as test cases, under the density functional theory and by means of chemical bonding techniques. Our results clearly reveal strong and localized noncovalent signatures, together with an enhanced orbital interaction, associated with CH−π and sulfur-mediated interactions governing the staggered formation. Bending the fullerene fragment is demonstrated to favor the stabilization in both homo- and heterodimers, in good accord with the depletion in the π-electron density calculated upon increasing the buckybowl curvature. The optimal buckybowl curvature for the highest interaction energy is, however, dependent on the type of supramolecular assembly (bowl-in-bowl vs staggered) and the concave region to which hemifullerene approaches truxTTF. Interestingly, two regimes are found as a function of buckybowl curvature for hemifullerene homodimers: bowl-in-bowl dispositions are calculated more stable at low curvatures whereas staggered dimers prevail for highly curved buckybowls. Our results highlight the potential of discrete CH−π and sulfur-mediated interactions to generate unconventional staggered supramolecular arrangements toward the development of a new and unexplored host–guest chemistry

Efficient Light Harvesters Based on the 10-(1,3-Dithiol-2-ylidene)anthracene Core

Three new push–pull chromophores based on the 10-(1,3-dithiol-2-ylidene)anthracene core were synthesized and fully characterized. The new chromophores display broad absorption spectra, nearly covering the whole visible region, with high extinction coefficients. Electrochemistry and theoretical calculations allowed the understanding of these singular electronic properties. The molecular structures were unambiguously confirmed by X-ray diffraction

Efficient Light Harvesters Based on the 10-(1,3-Dithiol-2-ylidene)anthracene Core

Three new push–pull chromophores based on the 10-(1,3-dithiol-2-ylidene)anthracene core were synthesized and fully characterized. The new chromophores display broad absorption spectra, nearly covering the whole visible region, with high extinction coefficients. Electrochemistry and theoretical calculations allowed the understanding of these singular electronic properties. The molecular structures were unambiguously confirmed by X-ray diffraction

Efficient Light Harvesters Based on the 10-(1,3-Dithiol-2-ylidene)anthracene Core

Three new push–pull chromophores based on the 10-(1,3-dithiol-2-ylidene)anthracene core were synthesized and fully characterized. The new chromophores display broad absorption spectra, nearly covering the whole visible region, with high extinction coefficients. Electrochemistry and theoretical calculations allowed the understanding of these singular electronic properties. The molecular structures were unambiguously confirmed by X-ray diffraction

Stable Green Electroluminescence from an Iridium Tris-Heteroleptic Ionic Complex

An ionic tris-heteroleptic iridium complex gives green light-emitting electrochemical cells (LECs) with unprecedented performances for this part of the visible spectrum. The devices are very bright (>1000 cd m^–2), efficient (∼3%), and stable (>55 h). The novel complex is prepared using a new and efficient synthetic procedure. We show that there is a mixed orbital formation originating from the two different orthometalating ligands resulting in photophysical properties that lie between those of its two bis-heteroleptic analogs. Therefore, tris-heteroleptic complexes provide new avenues for fine-tunning the emission properties and to bridge gaps between a series of bis-heteroleptic complexes

Efficient Light Harvesters Based on the 10-(1,3-Dithiol-2-ylidene)anthracene Core

Three new push–pull chromophores based on the 10-(1,3-dithiol-2-ylidene)anthracene core were synthesized and fully characterized. The new chromophores display broad absorption spectra, nearly covering the whole visible region, with high extinction coefficients. Electrochemistry and theoretical calculations allowed the understanding of these singular electronic properties. The molecular structures were unambiguously confirmed by X-ray diffraction