Theoretical Study of the 1:1 Complexes between Carbon Monoxide and Hypohalous Acids

First-principles definition of ionicity and covalency in molecules and solids

The notions of ionicity and covalency of chemical bonds, effective atomic charges, and decomposition of the cohesive energy into ionic and covalent terms are fundamental yet elusive. For example, different approaches give different values of atomic charges. Pursuing the goal of formulating a universal approach based on firm physical grounds (first-principles or non-empirical), we develop a formalism based on Wannier functions with atomic orbital symmetry and capable of defining these notions and giving numerically robust results that are in excellent agreement with traditional chemical thinking. Unexpectedly, in diamond-like boron phosphide (BP), we find charges of +0.68 on phosphorus and -0.68 on boron atoms, and this anomaly is explained by the Zintl-Klemm nature of this compound. We present a simple model that includes energies of the highest occupied cationic and lowest unoccupied anionic atomic orbitals, coordination numbers, and strength of interatomic orbital overlap. This model captures the essential physics of bonding and accurately reproduces all our results, including anomalous BP.

Ab initio investigation of the competition of pnicogen, halogen, and hydrogen bonds resulting from the interactions between cyanophosphine and hypohalous acids

CONTEXT

The complexes formed as a result of the interactions between cyanophosphine (CP, H2PCN) and hypohalous acid molecules (HOX, X = F, Cl, Br, and I) were studied by employing ab initio computations conducted at the MP2/aug-cc-pVTZ level. Three types of complexes were acquired (I, II, and III) as a result of the (O∙∙∙P) pnicogen bond, the (N∙∙∙H) hydrogen bond, and the (N∙∙∙X) halogen bond interaction, respectively. The results of harmonic vibrational frequency calculations with no imaginary frequencies confirmed the structures as minima. In addition, given the interaction energy of the complexes, hydrogen bond complexes of structure II have the highest stability compared to other structures. In all studied complexes, the strength of the interactions depended on the electronegativity of the halogen atoms. The characteristics and nature of the whole three types of complexes were examined and evaluated with natural bond orbital (NBO), atom in molecules (AIM), molecular electrostatic potential (MEP) maps, non-covalent interaction (NCI) index, and electron density difference (EDD) analyses.

METHOD

The optimization of all complexes and corresponding monomers was conducted through the ab initio method, employing the MP2 level along with the aug/cc-pVTZ basis set for all atoms, except for the iodine (I) atom, for which the aug-cc-pVTZ (PP) basis set was employed. Subsequent frequency calculations were executed to ascertain the minimum energy state of the complexes at the MP2 level and the aug/cc-pVTZ basis set, utilizing Gaussian09 software. The MEP maps of the monomers were generated using the analysis-surface suite (WFA-SAS) software package. To probe the orbital interactions within the studied complexes, NBO analysis was performed employing NBO software. The assessment of bond nature, topological features, and electron density values at critical points for the studied complexes was undertaken using AIMAll software. The NCI index was derived utilizing Multiwfn software, and its three-dimensional representation was rendered using VMD software.

Competition of hydrogen, tetrel, and halogen bonds in COCl2-HOX (X=F, Cl, Br, I) complexes

The present study investigates the competition between hydrogen, halogen, and tetrel bonds from the interaction of COCl₂ with HOX using quantum chemistry simulations at the MP2/aug-cc-pVTZ computational level, in which five configurations were optimized, including adducts I -V. Two hydrogen bonds, two halogen bonds, and two tetrel bonds were obtained for five forms of adducts. The compounds were investigated using spectroscopic, geometry, and energy properties. Adduct I complexes are more stable than others, and adduct V halogen bonded complexes are more stable than adduct II complexes. These results are in agreement with their NBO and AIM results. The stabilization energy of the XB complexes depends on the nature of both the Lewis acid and base. The stretching frequency of the O-H bond in adducts I, II, III, and IV displayed a redshift, and a blue shift was observed in adduct V. The results for the O-X bond showed a blue shift in adducts I and III and a red shift in adducts II, IV, and V. The nature and characteristics of three types of interactions are investigated via NBO analysis and atoms in molecules (AIM).

Theoretical treatment of IO-X (X = N2, CO, CO2, H2O) complexes

Iodine monoxide (IO) is an important component of the biogeochemical cycle of iodine. For instance, it is present in the troposphere, where it plays a crucial role in the physical chemical processes involving iodine containing compounds. Here, we present a theoretical study on a series of atmospherically relevant complexes of IO with N₂, CO, CO₂ and H₂O, where their structural and spectroscopic properties and their interaction energies are computed. Calculations are carried out by means of ab initio post Hartree-Fock (RCCSD(T) and RMP2) methods and density functional theory DFT (PBE0 and M05-2X) based approaches with and without the inclusion of dispersion correction. After comparison to RCCSD(T), we highlight the good performance of M05-2X(+D3) DFT in describing the bonding between IO and X (X = N₂, CO, CO₂, H₂O). Moreover, we found that the IO-X (X = N₂, CO, CO₂, H₂O) complexes are formed by non-covalent interactions between the two monomers. In sum, we characterized two types of complexes: I-bonded and O-bonded, where the former is more stable. The atmospheric implications of the present findings are also discussed such as in the formation of the iodine oxide particles (IOPs).

Using general computational chemistry strategy to unravel the reactivity of emerging pollutants: An example of sulfonamide chlorination

Increasing number of emerging pollutants in environments requires an effective approach which can facilitate the prediction of reactivity and provide insights into the reaction mechanisms. Computational chemistry is exactly the tool to fulfill this demand with its good performance in theoretical investigation of chemical reactions at molecular level. In this study, chlorination of sulfonamide antibiotics is used as an illustration to present a systematic strategy demonstrating how computational chemistry can be applied to investigate the reaction behavior of emerging pollutants. Sulfonamides is a class of micropollutants that contain the common structure of 4-aminobenzenesulfonmaide while differ in their heterocycles. Based on the calculated conceptual DFT indices, the reactive sites of sulfonamide are successfully predicted, which locate on their common structure of 4-aminobenzenesulfonmaide. Therefore, all sulfonamides follow the similar reaction pathway. Product identification by LTQ-Orbitrap MS further verifies the in silico prediction. Three critical pathways are discovered, i.e., S-N bond cleavage, Cl-substitution onto aniline-N, and the following rearrangement to lose -SO₂- group, among which Cl-substitution is the key step due to its lowest free energy barrier. Heterocycles impact the reaction rate by affecting the electronic density of aniline group. In general, the more electron-donating the heterocycle is, the more readily sulfonamides to be chlorinated.

Strengthening of halogen bond in XCl∙∙∙FH∙∙∙F- through cooperativity with a strong hydrogen bond and proton transfer

A theoretical calculation has been performed for the ternary complexes XCl∙∙∙FH∙∙∙F^- (X = CCH, CN, OH, NC, and F) and the corresponding binary complexes. The halogen bond in the dyad is very weak with the interaction energy less than 2.5 kcal/mol. Interestingly, the halogen bond gets a big enhancement when it combines with a very strong hydrogen bond in FH∙∙∙F^-, and the largest interaction energy is up to ∼25.6 kcal/mol in FCl∙∙∙FH∙∙∙F^-. The enhancement of halogen bond not only results in a larger elongation of X-Cl bond and a bigger redshift of the bond stretch vibration but also makes the blue-shifting halogen bond in NCCl∙∙∙FH be a red-shifting one in NCCl∙∙∙FH∙∙∙F^-. The halogen bond belongs to a purely close-shell interaction in the dyad, while it becomes a partially covalent interaction in XCl∙∙∙FH∙∙∙F^- (X = OH, NC, and F) with negative energy density. In FH∙∙∙F^-, the proton is shared between the two F atoms, however, this proton transfers towards the F^- end in XCl∙∙∙FH∙∙∙F^-.

Substituent effect of the stacking interaction between carbon monoxide and benzene

Noncovalent interactions (NCIs) between carbon monoxide and substituted benzene were investigated at the M06-2X/6-311++G(d,p) level. rThe results of interaction energy analysis indicated different effects for the electron-donating (-NH₂, -OH, -CH₃) and electron-withdrawing (-F, -CN, -NO₂) groups on the CO⋯PhX complex. Atoms in molecules analysis confirmed the NCIs between CO and PhX. NCI analysis revealed that these interactions belong to van der Waals interactions. The electron density shift of the complexes was investigated with electron density difference analysis. Ternary CO⋯PhX⋯Bz complexes were designed to study the interplay between CO⋯π and π⋯π stacking interactions.

Effect of Magnesium Bond on the Competition Between Hydrogen and Halogen Bonds and the Induction of Proton and Halogen Transfer

HOX (X=Cl, Br, I, and At) can engage in either a H-bond (HB) or halogen bond (XB) with a base-like HCN, NH₃ , and imidazole. Although the former is energetically preferred for X=Cl and Br, it is the XB that is more stable for At, with I showing little preference. MgY₂ forms a Mg-bond with the O atom of HOX, which grows stronger in the order X=Cl<Br<I<At and Y=F<Cl<Br. When all three molecules are combined, both the Mg and the H/X bonds are cooperatively strengthened to a large degree. Rather than causing a reversal in the HB/XB competition, the Mg-bond acts primarily to amplify the natural preference within the dimer. The Mg-bond induces a certain degree of transfer from O to N of the bridging atom in the H/X bond. Comparison is also made with the effects of a Be-bond.

Halogen Bonding Involving CO and CS with Carbon as the Electron Donor

MP2/aug'-cc-pVTZ calculations have been carried out to investigate the halogen-bonded complexes formed when CO and CS act as electron-pair donors through C to ClF, ClNC, ClCl, ClOH, ClCN, ClCCH, and ClNH₂. CO forms only complexes stabilized by traditional halogen bonds, and all ClY molecules form traditional halogen-bonded complexes with SC, except ClF which forms only an ion-pair complex. Ion-pair complexes are also found on the SC:ClNC and SC:ClCl surfaces. SC:ClY complexes stabilized by traditional halogen bonds have greater binding energies than the corresponding OC:ClY complexes. The largest binding energies are found for the ion-pair SC-Cl⁺:-Y complexes. The transition structures which connect the complex and the ion pair on SC:ClNC and SC:ClCl potential surfaces provide the barriers for inter-converting these structures. Charge-transfer from the lone pair on C to the σ-hole on Cl is the primary charge-transfer interaction stabilizing OC:ClY and SC:ClY complexes with traditional halogen bonds. A secondary charge-transfer occurs from the lone pairs on Cl to the in-plane and out-of-plane π antibonding orbitals of ClY. This secondary interaction assumes increased importance in the SC:ClNH₂ complex, and is a factor leading to its unusual structure. C-O and C-S stretching frequencies and 13C chemical shieldings increase upon complex formation with ClY molecules. These two spectroscopic properties clearly differentiate between SC:ClY complexes and SC-Cl⁺:-Y ion pairs. Spin-spin coupling constants 1xJ(C-Cl) for OC:ClY complexes increase with decreasing distance. As a function of the C-Cl distance, 1xJ(C-Cl) and ¹J(C-Cl) provide a fingerprint of the evolution of the halogen bond from a traditional halogen bond in the complexes, to a chlorine-shared halogen bond in the transition structures, to a covalent bond in the ion pairs.

Comparison of tetrel bonds and halogen bonds in complexes of DMSO with ZF3X (Z = C and Si; X = halogen)

A theoretical study of the complexes formed by dimethylsulfoxide (DMSO) with ZF₃X (Z = C and Si; X = halogen) has been performed at the MP2/aug-cc-pVTZ level.

Competition and cooperativity of σ-hole and π-hole intermolecular interactions between carbon monoxide and bromopentafluorobenzene

The electronic complementary relationship between C₆F₅Br and CO enables them to interact with each other via σ-hole and π-hole intermolecular interactions.

Halogen bonding. The role of the polarizability of the electron-pair donor

The nature of F–Br⋯X–R interactions (with X = Cl, Br, I and R = –H, –F) has been investigated through theoretical calculation of molecular potential electrostatic (MEP), molecular polarizability, atoms in molecules (AIM) analysis and energetic decomposition analysis (EDA).

Transition-metal-free, ambient-pressure carbonylative cross-coupling reactions of aryl halides with potassium aryltrifluoroborates

A transition-metal-free, ambient-pressure, and general methodology for carbonylative Suzuki coupling has been developed.

Complexes between hypohalous acids and phosphine derivatives. Pnicogen bond versus halogen bond versus hydrogen bond

The complexes of HOBr:PH2Y (Y=H, F, Cl, Br, CH3, NH2, OH, and NO2), HOCl:PH2F, and HOI:PH2F have been investigated with ab initio calculations at the MP2/aug-cc-pVTZ level. Four types of structures (1, 2, 3a, and 3b) were observed for these complexes. 1 is stabilized by an O⋯P pnicogen bond, 2 by a P⋯X halogen bond, 3a by a H⋯P hydrogen bond and a P⋯X pnicogen bond, and 3b by H⋯P and H⋯Br hydrogen bonds. Their relative stability is related to the halogen X of HOX and the substituent Y of PH2Y. These structures can compete with interaction energy of -10.22∼-29.40 kJ/mol. The HO stretch vibration shows a small red shift in 1, a small irregular shift in 2, but a prominent red shift in 3a and 3b. The XO stretch vibration exhibits a smaller red shift in 1, a larger red shift in 2, but an insignificant blue shift in 3a and 3b. The PY stretch vibration displays a red shift in 1 but a blue shift in 2, 3a, and 3b. The formation mechanism, stability, and properties of these structures have been analyzed with molecular electrostatic potentials, orbital interactions, and non-covalent interaction index.

Increased risk of dementia in patients exposed to nitrogen dioxide and carbon monoxide: a population-based retrospective cohort study

Background

The air pollution caused by vehicular emissions is associated with cognitive decline. However, the associations between the levels of nitrogen dioxide (NO₂) and carbon monoxide (CO) exposure and dementia remain poorly defined and have been addressed in only a few previous studies.

Materials and Methods

In this study, we obtained data on 29547 people from the National Health Insurance Research Database (NHIRD) of Taiwan, including data on 1720 patients diagnosed with dementia between 2000 and 2010, and we evaluated the risk of dementia among four levels of air pollutant. Detailed data on daily air pollution were available from January 1, 1998 to December 31, 2010. Yearly average concentrations of pollutants were calculated from the baseline to the date of dementia occurrence, withdrawal of patients, or the end of the study, and these data were categorized into quartiles, with Q1 being the lowest level and Q4 being the highest.

Results

In the case of NO₂, the adjusted hazard ratios (HRs) of dementia for all participants in Q2, Q3, and Q4 compared to Q1 were 1.10 (95% confidence interval (CI), 0.96–1.26), 1.01 (95% CI, 0.87–1.17), and 1.54 (95% CI, 1.34–1.77), and in the case of CO, the adjusted HRs were 1.07 (95% CI, 0.92–1.25), 1.37 (95% CI, 1.19–1.58), and 1.61 (95% CI, 1.39–1.85).

Conclusion

The results of this large retrospective, population-based study indicate that exposure to NO₂ and CO is associated with an increased risk of dementia in the Taiwanese population.

Competition between hydrogen and halogen bonding in the structures of 5,10-dihydroxy-5,10-dihydroboranthrenes

X-ray crystallographic and computational studies are reported for a series of boranthrenes, substituted with halogen atoms. The role of competitive hydrogen (O—H...O, O—H...F, C—H...O) and halogen (Cl...Cl, O...Br, F...F) bonding interactions on the molecular arrangement in the crystal structures is discussed. The structural analysis and calculations reveal that the O—H...O hydrogen bond in the unsubstituted derivative 5,10-dihydroxy-5,10-dihydroboranthrene, C12H10B2O2, is of moderate strength (ca−20 kJ mol−1), but weaker than that in the related thiophene derivative 4,8-dihydro-4,8-dihydroxy-p-diborino[2,3-b:5,6-b]dithiophene, C8H6B2O2S2(ca−40 kJ mol−1). This is due to shielding of the OH group by the H atoms in the β-position of the boranthrene unit. Structural diversity derived from the flexibility of the O—H...O hydrogen bond facilitates the occurrence of other competitive interactions. For instance, in the 1,6-difluoro derivative, C12H8B2F2O2, the crystal packing results from O—H...F and F...F interactions. In turn, the 1,6-dibromo derivative, C12H8B2Br2O2, is dominated by Br...O halogen-bond interactions. In the most interesting case, the 1,6-dichloro derivative, C12H8B2Cl2O2, molecular disorder leads to the formation of two different supramolecular arrangements co-existing in the crystal lattice, one based on the Cl...Cl and C—H...O bonds, and the other stabilized by O—H...O hydrogen bonds. Calculations performed with density-functional theory (DFT;CRYSTAL09) andPIXELmethodologies show that both lattices are characterized by similar energy values (ca−100 kJ mol−1). A mixed arrangement with random or short-range-ordered molecular orientations can also be expected.

A quantum chemical study of the structures, stability, and spectroscopy of halogen- and hydrogen-boned complexes between cyanoacetaldehyde and hypochlorous acids

The complexes of cyanoacetaldehyde and hypohalous acid (HOX, X=Cl, Br, and I) have been investigated. They can form six different structures (A, B, C, D, E, and F), the former three structures are mainly combined through a N(O)⋯X halogen bond and the latter three structures are maintained mainly by a N(O)⋯H hydrogen bond, although other weaker interactions are also present in most structures. The hydrogen-bonded structures are more stable than the respective halogen-bonded structures. The O-H and O-X bonds in the halogen- and hydrogen-bonded complexes are lengthened and show an observed red shift, while those in the weaker secondary interactions are contracted and display a small blue shift. The orbital interactions in NBO analysis and the electron densities in AIM analysis provide useful and reliable information for the strength of each type of interaction in different structures.

Competition of hydrogen, halogen, and pnicogen bonds in the complexes of HArF with XH2P (X=F, Cl, and Br)

A theoretical study of the complexes formed between HArF and XH2P (X=F, Cl, and Br) has been carried out using ab initio methods (MP2/aug-cc-pVDZ, MP2/aug-cc-pVTZ, and CCSD(T)/aug-cc-pVTZ). Three minima were found, which correspond to a hydrogen-bonded complex (I), a pnicogen-bonded complex (II), and a halogen-bonded complex (III). The pnicogen-bonded complex is the most stable, followed by the hydrogen-bonded complex, and the halogen-bonded complex is the least stable. The Ar-H bond is enhanced in FH2P-HArF-I complex and exhibits a blue shift, while it is weakened in ClH2P-HArF-I and BrH2P-HArF-I complexes and shows a red shift. A blue shift is also found for the distant Ar-H bond in the halogen-bonded and pnicogen-bonded complexes. These complexes have been understood with the electrostatic potentials and symmetry adapted perturbation theory (SAPT) method.

Competition between dihydrogen bond and beryllium bond in complexes between HBeH and HArF: a huge blue shift of distant H-Ar stretch

A novel interaction mechanism between HArF and BeH(2) has been validated and characterized with quantum chemical calculations at the MP2/aug-cc-pVQZ level. They can interact through beryllium bonding formed between the positively charged Be atom in BeH(2) and the negatively charged F atom in HArF, besides through dihydrogen bonding. The former (61.3 kcal/mol) is much stronger than the latter (5.9 kcal/mol). The red shift is found for the associated H-Ar stretch in the dihydrogen bonding, whereas the big blue shift is observed for the distant H-Ar stretch in the beryllium bonding. The blue shift of the distant H-Ar stretch is affected greatly by computational methods. It is calculated to be 712 cm(-1) at the CCSD(T)/6-311++G(3df,2p) level, which appears to be the largest blue shift validated for any weakly bound complex yet. The substitution effect on the beryllium bond is similar to that on hydrogen bonds. The Kr atom makes the beryllium bond weaken and the distant blue shift decrease. The nature and properties of beryllium bond have been analyzed with natural bond orbital (NBO), atoms in molecules (AIM), and energy decomposition.

Concerted interaction between pnicogen and halogen bonds in XCl-FH2P-NH3 (X=F, OH, CN, NC, and FCC)

We analyze the interplay between pnicogen-bonding and halogen-bonding interactions in the XCl-FH(2)P-NH(3) (X=F, OH, CN, NC, and FCC) complex at the MP2/aug-cc-pVTZ level. Synergetic effects are observed when pnicogen and halogen bonds coexist in the same complex. These effects are studied in terms of geometric and energetic features of the complexes. Natural bond orbital theory and Bader's theory of "atoms in molecules" are used to characterize the interactions and analyze their enhancement with varying electron density at critical points and orbital interactions. The physical nature of the interactions and the mechanism of the synergetic effects are studied using symmetry-adapted perturbation theory. By taking advantage of all the aforementioned computational methods, the present study examines how both interactions mutually influence each other.

Large blue shift of the H-Ar stretching frequency in hydrogen- and halogen-bonded complexes of HArF with dihalogen molecules

Quantum chemical calculations have been performed on the complexes formed between HArF and dihalogen molecules (XY=ClCl, ClF, BrCl, and BrF) at the MP2/6-311++G(2d,2p) level. For each complex, two minima were found, which correspond to one hydrogen-bonded complex and one halogen-bonded complex. The halogen-bonded complex with the F atom of HArF is more stable than the hydrogen-bonded complex with the H atom of HArF. A large blue shift of the H-Ar stretching frequency was observed in the hydrogen-bonded complex. However, in the halogen-bonded complex, in which the H-Ar bond is not involved in the interaction, a much large blue shift was observed for the same bond. The natural bond orbital and atoms in molecules analyses have been performed for these complexes. The energy decomposition analysis indicated that the electrostatic interaction plays a main contribution in formation of both complexes although the contribution from the charge-transfer interaction is also important.