Constructing, in silico, molecular self-aggregates and micro-hydrated complexes of oxirene and thiirene.

Context: Oxirene, surmised to exist in the interstellar medium, was synthesized in the laboratory only recently. The present study investigates theoretically to what extent the two exotic molecules, oxirene and its thia-analogue thiirene, are capable of forming molecular self-aggregates and undergo micro-hydration under cooperative hydrogen bonding as the tour de force. Cogent molecular descriptors, such as binding energies for cluster formation, molecular electrostatic potential (MESP), effective atomic charges, infrared spectroscopic response, criticality profiles from the quantum theory of atoms in molecules (QTAIM), hydrogen bond energies, and reduced density gradient (RDG) maps identifying non-covalent interactions (NCI), all in unison confirm theoretically the existence and characterize the aggregates.

Theoretical Appraisal of Cyclopropenone: Aggregation and Complexes with Water.

Cyclopropenone (HCCOCH, "CPN") is an exotic quasi-aromatic cyclic carbene that abounds in the interstellar medium (ISM). Astronomical observations suggest that (i) stagnate CPN exhibits a tendency to polymerize and that (ii) interactions may occur between CPN and water that is also ubiquitous in the ISM. In this light, density functional theory investigations reveal cooperative hydrogen bonding, which leads to stable polymeric conformations of (CPN), tracked up to = 14.

Cyclopropenylidene: Clustering and Interaction with Water Molecules.

Cyclopropenylidene (c-CH, abbreviated CPD) is a highly reactive, planar, partially aromatic carbene discovered in the interstellar medium, and, also recently, in the outer solar system. It is demonstrated herein on cogent quantum chemical grounds that CPD which possesses an electric dipole moment of 3.4 D is capable of forming stable dimer and trimer clusters through hydrogen-bonding.

Design and synthesis of piezochromic materials exploring intermolecular charge transfer: chalconoids bound to the -sulfonatocalix[6]arene macrocycle.

Solid-state systems composed of chalconoid encapsulated within -sulfonatocalix[6]arene (SCX6) scaffolds that exhibit mechanochromism and thermochromism have been developed. An introduction of a supramolecular host promises a variety of applications in diverse areas, which makes them fascinating. Largely hydrogen bonding as well as π···π interactions are responsible for the host-guest complexation.

H and C NMR chemical shifts of 2--alkylamino-naphthalene-1,4-diones.

H as well as C chemical shifts of 32 compounds of C (3) substituted 2-(-alkylamino)-3R-naphthalene-1,4-dione (where -alkyl: methyl, to octyl, R = H, Cl, Br, and CH) are investigated through H, C, DEPT, gDQCOSY, and gHSQCAD NMR experiments and M06-2X/6-311++G (d,p) density functional theory are discussed. Single crystal X-ray structure of Br-3, as well as 18 different derivatives of naphthalene-1,4-diones, are revealed for its inter and intra-molecular hydrogen bonding interactions.

Perethylated pillar[n]arenes versus pillar[n]arenes: theoretical perspectives.

In this article we obtain the electronic structure, H NMR, and the vibrational spectra of perethylated pillar[n]arene (EtPn) (n = 5-8, 10) macrocycles using the ωB97x-based density functional theory. A single cavitand structure endowed with the robust pillar-like architecture was derived for the EtPn (n = 5-7) hosts while for the EtP8 receptor, two conformers one possessing the single cavitand and other double cavitand structure having four hydroquinone monomeric units in each cavity were obtained as the local minima. A double cavitand conformer of the EtP8 was found to be ~ 50 kJ mol lower in energy than the single cavitand one which was attributed to the increased hydrogen bonding cooperativity and attractive H-H interactions.

Regioselectivity in nonsymmetric methyl pentyl Pillar[5]arene bound to non-symmetric axles.

The present work illustrates regioselective binding of nonsymmetric axle BuX (X = F, Cl, Br, CN) and 5-bromovaleronitrile (BVN) to the non-symmetric methyl pentyl pillar[5]arene (MPP5). Theoretical calculations reveal that the guest encapsulation within MPP5 is spontaneous and the conformer showing X weakly bound to pentyl rim of MPP5 is favoured over its other conformer wherein it interacts with methyl rim of the host. The noncovalent interactions namely C-H---π, C-H---X and H-H prevail over C-H⋯O hydrogen bonding in the complexes of MPP5.

Probing Binding of Ethylated Pillar[5]arene with Pentene and Chlorobutane Positional Isomers.

Host guest binding from alkyl-modified pillararene macrocycles has been of significant interest in a variety of applications in the domains of supramolecular chemistry. In this work, we analyze the selectivity in binding of the ethylated pillar[5]arene (EtP5) macrocycle with 1-pentene, and 2-pentene, and the 1- and 2-chlorobutane isomer guests employing the ωB97x-based density functional theory. EtP5 reveals stronger binding with 1-pentene the accompanying change of energy upon the complexation being 85.

Modeling protic dicationic ionic liquids based on quaternary ammonium, imidazolium or pyrrolidinium cations and bis(trifluoromethanesulfonyl)imide anion: Structure and spectral characteristics.

Protic dicationic ionic liquids (PDILs) have attracted growing attention owing to their applications in domains of electrochemistry, proton conducting materials and other diverse areas. In the present work protic dicationic ionic liquids (PDILs) comprising of quaternary ammonium-, imidazolium- or pyrrolidinium-dications and bis(trifluoromethanesulfonyl)imide (TfN‾) anion have been modelled as the dication-(TfN) complexes. Electronic structure, vibrational and H NMR spectra of these complexes have been derived employing the M06-2x density functional theory.

Understanding the Atmospheric Oxidation of HFE-7500 (CFCF(OCH)CF(CF)) Initiated by Cl Atom and NO Radical from Theory.

Kinetics and mechanistic pathways for atmospheric oxidation of HFE-7500 ( n-CFCF(OCHCH)CF(CF)) initiated by Cl atom and NO radical have been studied using density functional theory. Oxidative degradation pathways facilitated by H-abstraction from the -OCH or -CH groups in HFE-7500 have been considered. It has been shown that H-abstraction from the α-site (-OCH) is favored over other reaction pathways.

Unveiling Noncovalent Interactions in Imidazolium, Pyrrolidinium, or Quaternary Ammonium Cation and Acetate Anion Based Protic Ionic Liquids: Structure and Spectral Characteristics.

In the present work protic ionic liquids (PILs) composed of imidazolium-, quaternary ammonium-, or pyrrolidinium-dications and acetate (OAc) anion have been modeled as the dication-anion complexes through the M06-2x based density functional theory. It has been shown that cation-anion interaction energies are larger for the PILs containing the quaternary ammonium cation, which can be attributed to strong hydrogen bonding from the terminal ammonium protons. Underlying N-H···O and C-H···O hydrogen bonding, electrostatic, and van der Waals interactions are unraveled using the natural bond orbital analyses in conjunction with the quantum theory of atoms in molecules (QTAIM) and noncovalent interaction index reduced density gradient methods.

Exploring Chimeric Calix[4]tetrolarene Molecular Scaffolds: Theoretical Investigations.

The structure and spectral characteristics of the chimeric mixture of calixarene and pyrogallolarene (usually referred to as calix[4]tetrolarene) and its derivatives are studied employing the M06-2X-based density functional theory. Different conformers, viz., cone, partial cone, 1,2-alternate, and 1,3-alternate, were identified as the stationary point structures on their potential energy surfaces.

Distinct photophysical behaviour and transport of cell-impermeable [Ru(bpy)dppz] in live cells using cucurbit[7]uril as a delivery system.

Here, we report the delivery of a cell-impermeable [Ru(bpy)dppz] complex across a cell membrane using a cucurbit[7]uril molecular container. Encapsulation of complex 1 in the cucurbit[7]uril cavity showed an 830-fold enhancement in the luminescence intensity of the non-emissive complex in aqueous solution. This molecular light-switch effect stems from the incorporation of the dppz ligand of 1 inside the CB7 cavity and can be attributed to long range coulombic forces between Ru and the carbonyl portal of CB7 via CHO interactions.

Molecular Recognition, Conformational Behavior, and Spectral Characteristics of Oxatub[4]arene Macrocycle.

In the present work, we analyze molecular recognition behavior of synthetic hydroxylated oxatub[4]arene (TA4) receptor toward the methyl viologen in different redox states. The supramolecular binding of methyl viologen guest toward TA4 macrocyclic scaffold has been studied employing the dispersion corrected ωB97X-D based density functional theory. The methyl viologen in dicationic and neutral forms revealed distinct features in electronic, H nuclear magnetic resonance, and infrared spectra.

Noncovalent interactions underlying binary mixtures of amino acid based ionic liquids: insights from theory.

Mixtures of ionic liquids formed by blending a common 1-methyl-3-butylimidazolium [Bmim] cation with the dicarboxylic amino acid anions viz., aspartic acid [Asp], asparagine [Asn], glutamic acid [Glu], and glutamine [Gln], have been investigated by employing dispersion corrected density functional theory. Binary mixtures of [Bmim][Asp][Asn] and [Bmim][Glu][Gln] ionic liquids emerge with distinct structural patterns.

Host-Guest Interactions Accompanying the Encapsulation of 1,4-Diazabicyclo[2.2.2]octane within endo-Functionalized Macrocycles.

The binding of novel endofunctionalized bis-urea/thiourea molecular receptors toward neutral 1,4-diazabicyclo[2.2.2]octane (DABCO) demonstrates stronger binding of the bis-thiourea macrocycles than for their urea analogues by employing M06-2X/6-31+G(d,p)-based density functional theory.

Noncovalent Interactions Accompanying Encapsulation of Resorcinol within Azacalix[4]pyridine Macrocycle.

Electronic structure and noncovalent interactions within the inclusion complexes of resorcinol and calix[4]pyridine (CXP[4]) or azacalix[4]pyridine (N-CXP[4]) macrocycles have been analyzed by employing hybrid M06-2X density functional theory. It has been demonstrated that substitution of a heteroatom (-NH-) at the bridging position of the CXP[4] alters the shape of the cavity from a "box-shaped" to funnel-like one. Penetration of resorcinol guest within the CXP[4] cavity renders a "butterfly-like" structure to the complex, whereas the N-CXP[4] complex reveals distorted geometry with the guest being nearer to one of the pyridine rings at the upper rim of the host.

Kinetics and Mechanistic Investigations of Atmospheric Oxidation of HFO-1345fz by OH Radical: Insights from Theory.

HFO-1345fz (CFCFCH═CH or 3,3,4,4,4-pentafluoro-1-butene) belongs to a class of hydrofluoro-olefins and represents a new generation of potential foam expansion agents. Its atmospheric impact and environmental acceptability can be estimated from the studies of kinetics and mechanism of its oxidative degradation. The molecular insights accompanying the reaction pathways in terms of the characterization of intermediates or products and radiative properties should prove useful for large-scale industrial applications.

Density Functional Investigations on the Selective Binding of an endo-Functionalized Bis-urea Macrocycle.

The preferential binding of syn and anti configurational isomers of endo-functionalized bis-urea molecular receptor to 1,2-dinitrobenzene (G1) and 1,4-dioxane (G2) guests has been explained using dispersion-corrected M06-2X-based density functional theory. The host-guest binding is facilitated via hydrogen bonding, C-H···π, dipole-dipole, C···C and O···O (chalcogen-chalcogen) interactions. The formation of an inclusion complex is spontaneous and thermodynamically favorable.

Understanding Binding of Cyano-Adamantyl Derivatives to Pillar[6]arene Macrocycle from Density Functional Theory.

The ωB97X-based density functional theory has been employed to characterize molecular interactions between adamantane carbonitrile (ACN) or adamantane methyl carbonitrile (AMCN) and the ethylated pillar[6]arene (EtP[6]) molecular receptor. The inclusion complexes in 1:1 stoichiometry are stabilized through noncovalent interactions such as hydrogen bonding, C-H···π and dipole-dipole interactions. Gibbs free energies accompanying the encapsulation of ACN or AMCN within EtP[6] revealed that the formation of complex is spontaneous and thermodynamically favorable.

Probing Molecular Interactions in Functionalized Asymmetric Quaternary Ammonium-Based Dicationic Ionic Liquids.

Electronic structure, binding energies, and spectral characteristics of functionalized asymmetric dicationic ionic liquids (DILs) composed of quaternary ammonium cations substituted with the ethoxyethyl and allyl/3-phenylpropyl/methoxyethoxyethyl/pentyl functionalities on two different nitrogen centers of the dication and the bis(trifluoromethanesulfonyl)imide (TfN) anion were derived employing the dispersion-corrected density functional theory. DILs based on methoxyethoxyethyl-substituted cation reveal stronger binding toward the TfN anion. The measured glass transition temperatures are found to be strongly dependent on the cation-anion binding facilitated through noncovalent interactions with dominant contributions from the electrostatics and hydrogen bonding.

Cooperative Hydrogen Bonding, Molecular Electrostatic Potentials, and Spectral Characteristics of Partial Thia-Substituted Calix[4]arene Macrocycles.

Structure and spectral characteristics of the 2,14-dithiacalix[4]arene and its homooxa derivatives are obtained employing the dispersion-corrected ωB97X-D-based density functional theory. The conformational behavior of these receptors is governed by the nature and number of substituents at the bridging positions. The partial thia-substituted calix[4]arene scaffolds reveal the electron-rich regions reside near heteroatoms which emerge with deeper minima in molecular electrostatic potential topography.

Encaged molecules in external electric fields: A molecular "tug-of-war".

Response of polar molecules CH3OH and H2O2 and a non-polar molecule, CO2, as "guests" encapsulated in the dodecahedral water cage (H2O)20 "host," to an external, perturbative electric field is investigated theoretically. We employ the hybrid density-functionals M06-2X and ωB97X-D incorporating the effects of damped dispersion, in conjunction with the maug-cc-pVTZ basis set, amenable for a hydrogen bonding description. While the host cluster (cage) tends to confine the embedded guest molecule through cooperative hydrogen bonding, the applied electric field tends to rupture the cluster-composite by stretching it; these two competitive effects leading to a molecular "tug-of-war.

Electronic Structure, NMR, Spin-Spin Coupling, and Noncovalent Interactions in Aromatic Amino Acid Based Ionic Liquids.

Noncovalent interactions accompanying phenylalanine (Phe), tryptophan (Trp), and tyrosine (Tyr) amino acids based ionic liquids (AAILs) composed of 1-methyl-3-butyl-imidazole and its methyl-substituted derivative as cations have been analyzed employing the dispersion corrected density functional theory. It has been shown that cation-anion binding in these bioionic ILs is primarily facilitated through hydrogen bonding in addition to lp---π and CH---π interactions those arising from aromatic moieties which can be probed through (1)H and (13)C NMR spectra calculated from the gauge independent atomic orbital method. Characteristic NMR spin-spin coupling constants across hydrogen bonds of ion pair structures viz.