101
|
Zhang B, Altarawy D, Barnes T, Turney JM, Schaefer HF. Janus: An Extensible Open-Source Software Package for Adaptive QM/MM Methods. J Chem Theory Comput 2019; 15:4362-4373. [DOI: 10.1021/acs.jctc.9b00182] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
102
|
Abbott AS, Turney JM, Zhang B, Smith DGA, Altarawy D, Schaefer HF. PES-Learn: An Open-Source Software Package for the Automated Generation of Machine Learning Models of Molecular Potential Energy Surfaces. J Chem Theory Comput 2019; 15:4386-4398. [DOI: 10.1021/acs.jctc.9b00312] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
103
|
Bowman MC, Douberly GE, Schaefer HF. Convergent energies and anharmonic vibrational spectra of Ca 2H 2 and Ca 2H 4 constitutional isomers. Phys Chem Chem Phys 2019; 21:10914-10922. [PMID: 31086933 DOI: 10.1039/c9cp01643k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Three constitutional isomers of both Ca2H2 and Ca2H4 have been characterized with molecular electronic structure theory. Correlation methods as complete as CCSDT(Q) and basis sets as large as cc-pwCV5Z have been used to converge the relative energies within chemical accuracy (≤1 kcal mol-1). Anharmonic vibrational frequencies were computed using second-order vibrational perturbation theory employing CCSD(T)/cc-pwCVTZ cubic and quartic force-fields and a CCSD(T)/cc-pwCVQZ quadratic force field. The monobridged [Ca(μ2-H)CaH] and dibridged [Ca(μ2-H)2Ca] isomers of Ca2H2 were predicted to lie 6.5 and 12.9 kcal mol-1 below the energy of the classical HCaCaH linear isomer, respectively. Despite the energetic favorability of the bridged Ca2H2 isomers, we conclude (surprisingly) that only the higher energy linear structure has been observed in the laboratory. At 0 K, the tribridged [Ca(μ2-H)3CaH] isomer of Ca2H4 is predicted to be enthalpically favored by 0.9 kcal mol-1 in comparison to the enthalpy of the dibridged [HCa(μ2-H)2CaH] structure. Comparison of experiment with our computed frequencies suggests that the observed vibrational features arise from both the dibridged and the tribridged Ca2H4 structures.
Collapse
|
104
|
Dey S, Manogaran D, Manogaran S, Schaefer HF. Substituent effects on the aromaticity of benzene-An approach based on interaction coordinates. J Chem Phys 2019; 150:214108. [PMID: 31176350 DOI: 10.1063/1.5090588] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Benzene and 23 monosubstituted and 32 disubstituted derivatives of benzene were optimized for minimum energy structures using the B3LYP/cc-pVTZ method. The force fields of all the compounds were evaluated at their optimized geometries using the same method and basis set. In order to understand the effect of substitution(s) on the aromaticity of benzene, the aromaticity index based on interaction coordinates (AIBIC) values were computed for each and the change from the benzene value was obtained. This difference, the substituent effect based on interaction coordinates (SEBIC), quantifies the effect of the substituent on the aromaticity of benzene ring satisfactorily. It is found that the AIBIC of disubstituted benzenes (XC6H4Y) could be predicted well by adding the respective SEBIC(C6H5X) and SEBIC(C6H5Y) values to the AIBIC of benzene. The projected force fields of the meta and para fragments of the monosubstituted benzenes when chosen properly contain the information about the directing influence of the substituent in terms of the electron density based on interaction coordinates (EDBIC). When the EDBIC(para) > EDBIC(meta) relative to benzene, the substituent is ortho-para directing, while when the reverse is true, it is meta directing. The effect of conformational changes on aromaticity has been studied using aminophenols and dihydroxybenzenes. The additivity rule and the EDBIC concept work adequately well in that the methods can have several useful practical applications that will benefit various areas of science. A good understanding of the substituent effects and the ability to predict them should add a new dimension to the applications of AIBIC.
Collapse
|
105
|
Abstract
A cornucopia of very high-level theoretical methods has been used to study cyclobutyne, a molecule that has been the center of much speculation. We conclude that cyclobutyne is a transition state in its singlet ground state, based on new coupled cluster and multireference computations presented in this research. This is substantially different from other theoretical studies proposing the existence of singlet cyclobutyne as a minimum. The singlet cyclobutyne transition state ( C2 v) exhibits a ring puckering imaginary vibrational mode, leading to two equivalent minima, cyclopropylidenemethylenes in C s symmetry, with a barrier height of ∼23 kcal/mol. In contrast with previous studies, singlet cyclopropylidenemethylene in C2 v symmetry was predicted to be a transition state, not a minimum. Triplet cyclobutyne is a genuine minimum and higher-lying than the lowest singlet state by ∼15 kcal/mol. New computations give the total ring strain of the singlet cyclobutyne to be 101 kcal/mol, with an in-plane π-bond strain of 71 kcal/mol.
Collapse
|
106
|
Franke PR, Brice JT, Moradi CP, Schaefer HF, Douberly GE. Ethyl + O2 in Helium Nanodroplets: Infrared Spectroscopy of the Ethylperoxy Radical. J Phys Chem A 2019; 123:3558-3568. [DOI: 10.1021/acs.jpca.9b01867] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
107
|
Villegas-Escobar N, Poater A, Solà M, Schaefer HF, Toro-Labbé A. Decomposition of the electronic activity in competing [5,6] and [6,6] cycloaddition reactions between C 60 and cyclopentadiene. Phys Chem Chem Phys 2019; 21:5039-5048. [PMID: 30762038 DOI: 10.1039/c8cp07626j] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Fullerenes, in particular C60, are important molecular entities in many areas, ranging from material science to medicinal chemistry. However, chemical transformations have to be done in order to transform C60 in added-value compounds with increased applicability. The most common procedure corresponds to the classical Diels-Alder cycloaddition reaction. In this research, a comprehensive study of the electronic activity that takes place in the cycloaddition between C60 and cyclopentadiene toward the [5,6] and [6,6] reaction pathways is presented. These are competitive reaction mechanisms dominated by σ and π fluctuating activity. To better understand the electronic activity at each stage of the mechanism, the reaction force (RF) and the symmetry-adapted reaction electronic flux (SA-REF, JΓi(ξ)) have been used to elucidate whether π or σ bonding changes drive the reaction. Since the studied cycloaddition reaction proceeds through a Cs symmetry reaction path, two SA-REF emerge: JA'(ξ) and JA''(ξ). In particular, JA'(ξ) mainly accounts for bond transformations associated with π bonds, while JA''(ξ) is sensitive toward σ bonding changes. It was found that the [6,6] path is highly favored over the [5,6] with respect to activation energies. This difference is primarily due to the less intensive electronic reordering of the σ electrons in the [6,6] path, as a result of the pyramidalization of carbon atoms in C60 (sp2 → sp3 transition). Interestingly, no substantial differences in the π electronic activity from the reactant complex to the transition state structure were found when comparing the [5,6] and [6,6] paths. Partition of the kinetic energy into its symmetry contributions indicates that when a bond is being weakened/broken (formed/strengthened) non-spontaneous (spontaneous) changes in the electronic activity occur, thus prompting an increase (decrease) of the kinetic energy. Therefore, contraction (expansion) of the electronic density in the vicinity of the bonding change is expected to take place.
Collapse
|
108
|
Galabov B, Koleva G, Hadjieva B, Schaefer HF. π-Hydrogen Bonding Probes the Reactivity of Aromatic Compounds: Nitration of Substituted Benzenes. J Phys Chem A 2019; 123:1069-1076. [PMID: 30624929 DOI: 10.1021/acs.jpca.8b12508] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The shifts of phenol O-H stretching vibration frequencies [Δν(OH)exp] upon π-hydrogen bonding with aromatic compounds is proposed as a spectroscopic probe of the reactivity of aromatic substrates toward electrophiles. A single infrared spectrum reflecting the Δν(OH)exp shift for an aromatic species in a reference solvent (CCl4 in this study) provides a good estimate of reactivity. The methodology is applied in rationalizing reactivity trends for the BF3 catalyzed nitration by methylnitrate in nitromethane of 20 aromatic reactants, including benzene, 11 methylbenzenes, several monoalkyl benzenes, the four halobenzenes, and anisole. Literature kinetic data are employed in the analysis. Very good correlations between relative rates of nitration and Δν(OH)exp are obtained. The approach is best applied to reactions, where the initial interactions between the reactants controls the rates. A new theoretical quantity, the shifts (with respect to benzene) of the molecular electrostatic potential at 1.5 Å over the centroid of the aromatic ring [Δ V(1.5)] is defined and shown to provide a good description of substituent effects on properties of the aromatic species. B3LYP density functional and MP2 ab initio methods combined with the 6-311++G(3df,2pd) basis set are employed in evaluating the Δ V(1.5) values.
Collapse
|
109
|
Tang M, Chen X, Xie Y, Schaefer HF. Hydrogen Abstraction Reaction H2Se + OH → H2O + SeH: Comparison with the Analogous Hydrogen Sulfide and Water Reactions. Inorg Chem 2019; 58:2069-2079. [DOI: 10.1021/acs.inorgchem.8b03140] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
110
|
Zhang Y, Xie Y, Schaefer HF, Wu JIC. Stabilizing Borinium Cations [X-B-X] + through Conjugation and Hyperconjugation Effects. Inorg Chem 2019; 58:243-249. [PMID: 30565466 DOI: 10.1021/acs.inorgchem.8b02316] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Borinium, a two-coordinated boron cation, is a strong Lewis acid that was thought difficult to prepare due to a lower number of coordinating ligands and susceptibility toward nucleophilic reactions. Recently a dimesityl borinium cation (Mes2B+) with high thermal stability has been synthesized and characterized by Shoji and co-workers. These findings suggest that, despite being extremely electron-demanding, borinium cations might be stabilized with certain substituted function groups. In the present study, we have studied a series of the borinium cations [X-B-X]+ with different substituted groups using the NBO and the BLW methods. Our computations revealed that both π-conjugation and hyperconjugation effects can effectively stabilize substituted borinium cations [X-B-X]+. Substituents such as X = C═CH2 stabilize the borinium center through highly delocalized π-bonding, involving the formally "empty" boron p x and p y orbitals. We suggest the borinium cations [X-B-X]+ with X = cyc-N(CH)2 and especially X = C═CH2 as possible synthetic targets of novel borinium cations.
Collapse
|
111
|
Zhang L, Zhang X, Wu YD, Xie Y, Fukuto JM, Schaefer HF. The reaction of alkyl hydropersulfides (RSSH, R = CH 3 and tBu) with H 2S in the gas phase and in aqueous solution. Phys Chem Chem Phys 2019; 21:537-545. [PMID: 30307004 DOI: 10.1039/c8cp05503c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The RSSH + H2S → RSH + HSSH reaction has been suggested by numerous labs to be important in H2S-mediated biological processes. Seven different mechanisms for this reaction (R = CH3, as a model) have been studied using the DFT methods (M06-2X and ωB97X-D) with the Dunning aug-cc-pV(T+d)Z basis sets. The reaction of CH3SSH with gas phase H2S has a very high energy barrier (>45 kcal mol-1), consistent with the available experimental observations. A series of substitution reactions R1-S-S-H + -S-R2 (R1 = Me, tBu, Ad, R2 = H, S-Me, S-tBu, S-Ad) have been studied. The regioselectivity is largely affected by the steric bulkiness of R1, but is much less sensitive to R2. Thus, when R1 is Me, all -S-R2 favorably attack the internal S atom, leading to R1-S-S-R2. While for R1 = tBu, Ad, all -S-R2 significantly prefer to attack the external S atom to form -S-S-R2. These results are in good agreement with the experimental observations.
Collapse
|
112
|
Aroeira GJR, Abbott AS, Elliott SN, Turney JM, Schaefer HF. The addition of methanol to Criegee intermediates. Phys Chem Chem Phys 2019; 21:17760-17771. [DOI: 10.1039/c9cp03480c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
High level ab initio methods are employed to study the addition of methanol to the simplest Criegee intermediates and its methylated analogue. Kinetic rate constants over a range of temperatures are computed and compared to experimental results.
Collapse
|
113
|
Wang Y, Xie Y, Wei P, Schaefer HF, Robinson GH. Redox chemistry of an anionic dithiolene radical. Dalton Trans 2019; 48:3543-3546. [DOI: 10.1039/c8dt04989k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The redox reactivity of a stable anionic dithiolene radical has been explored, giving the corresponding dithiolate and neutral dithiolene dimers.
Collapse
|
114
|
Huang L, Li J, Li G, Xie Y, King RB, Schaefer HF. Alternative modes of bonding of C 4F 8 units in mononuclear and binuclear iron carbonyl complexes. NEW J CHEM 2019. [DOI: 10.1039/c9nj00882a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The lowest energy C4F8Fe(CO)4 structure is not the experimentally known ferracyclopentane complex but instead isomeric (perfluorobutene)iron tetracarbonyls. However, activation energies for the fluorine shifts required to form the latter isomers are very high. The lowest energy (C4F8)2Fe2(CO)n (n = 7, 6) structures have bridging perfluorocarbene and terminal perfluoroolefin ligands.
Collapse
|
115
|
Chen J, Feng H, Xie Y, King RB, Schaefer HF. Higher spin states in some low-energy bis(tetramethyl-1,2-diaza-3,5-diborolyl) sandwich compounds of the first row transition metals: boraza analogues of the metallocenes. NEW J CHEM 2019. [DOI: 10.1039/c8nj05517c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Density functional studies on (Me4B2N2CH)2M (M = Ti, V, Cr, Mn, Fe, Co, Ni) show low-energy sandwich structures for all seven metals. The lowest-energy such Cr and Mn derivatives have higher spin states than the corresponding metallocenes.
Collapse
|
116
|
Franke PR, Moore KB, Schaefer HF, Douberly GE. tert-Butyl peroxy radical: ground and first excited state energetics and fundamental frequencies. Phys Chem Chem Phys 2019; 21:9747-9758. [DOI: 10.1039/c9cp01476d] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The lowest adiabatic electronic transition origin and fundamental vibrational frequencies are computed, with high accuracy, for the tert-butyl peroxy radical.
Collapse
|
117
|
Gong S, Chen Y, Luo Q, Schaefer HF. The conformational preferences of polychlorocyclohexanes. NEW J CHEM 2019. [DOI: 10.1039/c9nj02997d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
A simple but precise model equation to get accurate conformational energies of polychlorocyclohexane conformations.
Collapse
|
118
|
Wiens AE, Copan AV, Schaefer HF. Multi-fidelity Gaussian process modeling for chemical energy surfaces. Chem Phys Lett 2019. [DOI: 10.1016/j.cpletx.2019.100022] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
119
|
Jiang H, Sun TY, Chen Y, Zhang X, Wu YD, Xie Y, Schaefer HF. Designing new Togni reagents by computation. Chem Commun (Camb) 2019; 55:5667-5670. [DOI: 10.1039/c9cc01320b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
New trifluoromethylating reagents are designed based on trans influence and steric effect.
Collapse
|
120
|
Wolf ME, Zhang B, Turney JM, Schaefer HF. A comparison between hydrogen and halogen bonding: the hypohalous acid–water dimers, HOX⋯H2O (X = F, Cl, Br). Phys Chem Chem Phys 2019; 21:6160-6170. [DOI: 10.1039/c9cp00422j] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Hypohalous acids (HOX) are a class of molecules that play a key role in the atmospheric seasonal depletion of ozone and have the ability to form both hydrogen and halogen bonds.
Collapse
|
121
|
Duncan Lyngdoh RH, Schaefer HF, King RB. Metal-Metal (MM) Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc. Chem Rev 2018; 118:11626-11706. [PMID: 30543419 DOI: 10.1021/acs.chemrev.8b00297] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This survey of metal-metal (MM) bond distances in binuclear complexes of the first row 3d-block elements reviews experimental and computational research on a wide range of such systems. The metals surveyed are titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc, representing the only comprehensive presentation of such results to date. Factors impacting MM bond lengths that are discussed here include (a) the formal MM bond order, (b) size of the metal ion present in the bimetallic core (M2) n+, (c) the metal oxidation state, (d) effects of ligand basicity, coordination mode and number, and (e) steric effects of bulky ligands. Correlations between experimental and computational findings are examined wherever possible, often yielding good agreement for MM bond lengths. The formal bond order provides a key basis for assessing experimental and computationally derived MM bond lengths. The effects of change in the metal upon MM bond length ranges in binuclear complexes suggest trends for single, double, triple, and quadruple MM bonds which are related to the available information on metal atomic radii. It emerges that while specific factors for a limited range of complexes are found to have their expected impact in many cases, the assessment of the net effect of these factors is challenging. The combination of experimental and computational results leads us to propose for the first time the ranges and "best" estimates for MM bond distances of all types (Ti-Ti through Zn-Zn, single through quintuple).
Collapse
|
122
|
Bowman MC, Burke AD, Turney JM, Schaefer HF. Mechanisms of the Ethynyl Radical Reaction with Molecular Oxygen. J Phys Chem A 2018; 122:9498-9511. [PMID: 30421915 DOI: 10.1021/acs.jpca.8b09862] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The ethynyl radical, •C2H, is a key intermediate in the combustion of various alkynes. Once produced, the ethynyl radical will rapidly react with molecular oxygen to produce a variety of products. This research presents the first comprehensive high level theoretical study of the reaction of the •C2H (2Σ+) radical with molecular oxygen (3Σg-). Correlation methods as complete as CCSDT(Q) were used; basis sets as large as cc-pV6Z were adopted. Focal point analysis was employed to approach relative energies within the bounds of chemical accuracy (≤1 kcal mol-1). Two dominate reaction pathways from the ethynyl peroxy radical include oxygen-oxygen cleavage from the ethynyl peroxy radical that is initially formed to produce HCCO (2A″) and O (3P) and an isomerization of the ethynyl peroxy radical to eventually yield HCO (2A') and CO (1Σ+). The branching ratio between these two competitive reaction pathways was determined to be 1:1 at 298 K. Minor reaction pathways leading to the production of CO2 (1Σg+) and CH (2Π, 4Σ-, 2Δ) were also characterized. The absence of CCO (3Σ-) and OH (2Π) was explained in terms competition with more accessible reaction pathways.
Collapse
|
123
|
Misiewicz JP, Noonan JA, Turney JM, Schaefer HF. The non-covalently bound SOH 2O system, including an interpretation of the differences between SOH 2O and O 2H 2O. Phys Chem Chem Phys 2018; 20:28840-28847. [PMID: 30420992 DOI: 10.1039/c8cp05749d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Despite the interest in sulfur monoxide (SO) among astrochemists, spectroscopists, inorganic chemists, and organic chemists, its interaction with water remains largely unexplored. We report the first high level theoretical geometries for the two minimum energy complexes formed by sulfur monoxide and water, and we report energies using basis sets as large as aug-cc-pV(Q+d)Z and correlation effects through perturbative quadruple excitations. One structure of SOH2O is hydrogen bonded and the other chalcogen bonded. The hydrogen bonded complex has an electronic energy of -2.71 kcal mol-1 and a zero kelvin enthalpy of -1.67 kcal mol-1, while the chalcogen bonded complex has an electronic energy of -2.64 kcal mol-1 and a zero kelvin enthalpy of -2.00 kcal mol-1. We also report the transition state between the two structures, which lies below the SOH2O dissociation limit, with an electronic energy of -1.26 kcal mol-1 and an enthalpy of -0.81 kcal mol-1. These features are much sharper than for the isovalent complex of O2 and H2O, which only possesses one weakly bound minimum, so we further analyze the structures with open-shell SAPT0. We find that the interactions between O2 and H2O are uniformly weak, but the SOH2O complex surface is governed by the superior polarity and polarizability of SO, as well as the diffuse electron density provided by sulfur's extra valence shell.
Collapse
|
124
|
Zhou D, Li G, Moore KB, Xie Y, Peterson KA, Schaefer HF. Noncovalent Interactions between Molecular Hydrogen and the Alkali Fluorides: H-H···F-M (M = Li, Na, K, Rb, Cs). High Level Theoretical Predictions and SAPT Analysis. J Chem Theory Comput 2018; 14:5118-5127. [PMID: 30199640 DOI: 10.1021/acs.jctc.8b00461] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Various types of hydrogen bonds have been recognized during the past century. In this research, a new type of noncovalent interaction, the dipole-induced hydrogen bond formed between a hydrogen molecule and an alkali halide, H-H···F-M, is studied. Proposed by Zhang and co-workers ( Phys. Chem. Chem. Phys. 2015, 17, 20361), these systems are extensively investigated initially using the "gold standard" CCSD(T) method in conjunction with augmented correlation-consistent polarized core-valence basis sets up to quadruple-ζ. The full triple excitations CCSDT method has been used to further refine the energies. Several properties including geometries, bond energies, vibrarional frequencies, charge distributions, and dipole moments have been reported. The earlier Zhang research considered only the linear H-H···F-M structures. However, we find these linear stationary points to be separated by very small barriers from the much lower lying bent C s structures. The CCSDT/aug-cc-pCVQZ(-PP) method predicts the dissociation energies for bent H-H···F-M (M = Li, Na, K, Rb, Cs) are 2.76, 2.96, 3.00, 2.89, and 2.49 kcal mol-1, respectively, suggesting that the H···F hydrogen bond becomes gradually stronger when alkali metal M goes down the periodic table from Li to K but becomes slightly weaker for Rb and even more for Cs. This Li < Na < K > Rb > Cs order is consistent with that for the dipole moments for the isolated MF (M = Li, Na, K, Rb, Cs) diatomics. Symmetry adapted perturbation theory (SAPT) is used to understand these unusual noncovalent interactions.
Collapse
|
125
|
Hoobler PR, Turney JM, Agarwal J, Schaefer HF. Fundamental Vibrational Analyses of the HCN Monomer, Dimer and Associated Isotopologues. Chemphyschem 2018; 19:3257-3265. [PMID: 30270472 DOI: 10.1002/cphc.201800728] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Indexed: 11/06/2022]
Abstract
In this work we provide high level ab initio treatments of the structures, vibrational frequencies, and electronic energies of the HCN monomer and dimer systems along with several isotopologues. The plethora of information related to this system within the literature is summarized and serves as a basis for comparison with the results of this paper. The geometry of the dimer and monomer are reported at the all electroncoupled-cluster singles, doubles, and perturbative triples level of theory [AE-CCSD(T)] with the correlation consistent quadruple-zeta quality basis sets with extra core functions (cc-pCVQZ) from Dunning. The theoretical geometries and electronic structures are further analyzed through the use of the Natural Bond Orbital (NBO) method and Natural Resonance Theory (NRT). At the AE-CCSD(T)/cc-pCVQZ level of theory, the full cubic with semi-diagonal quartic force field for nine dimer and four monomer isotopologues (the parent isotopologue along with 15 N, 13 C, and D derivatives) were obtained to treat the anharmonicity of the vibrations via second order vibrational perturbation theory (VPT2). Lastly, the enthalpy change associated with the formation of the dimer from two monomer units was determined using the focal point analysis. Computations including coupled-cluster through perturbative quadruples as well as basis sets up to six-zeta quality, including core functions (cc-pCVXZ, X=D,T,Q,5,6) were used to extrapolate to the AE-CCSDT(Q)/CBS energy associated with this hydrogen-bond forming process. After appending anharmonic zero-point vibrational, relativistic, and diagonal Born-Oppenheimer corrections, we report a value of -3.93 kcal mol-1 for the enthalpy of formation. To our knowledge, each set of results (geometries, vibrational frequencies, and energetics) reported in this study represents the highest-level and most reliable theoretical predictions reported for this system.
Collapse
|