Halogen-bond and hydrogen-bond interactions between three benzene derivatives and dimethyl sulphoxide

Abstract

Halogen-bonds, like hydrogen-bonds, are a kind of noncovalent interaction and play an important role in diverse fields including chemistry, biology and crystal engineering. In this work, a comparative study was carried out to examine the halogen/hydrogen-bonding interactions between three fluoro-benzene derivatives and dimethyl sulphoxide (DMSO). A number of conclusions were obtained by using attenuated total reflection infrared spectroscopy (ATR-IR), nuclear magnetic resonance (NMR) and ab initio calculations. Electrostatic surface potential, geometry, energy, vibrational frequency, intensity and the natural population analysis (NPA) of the monomers and complexes are studied at the MP2 level of theory with the aug-cc-pVDZ basis set. First, the interaction strength decreases in the order C6F5H-DMSO ∼ ClC6F4H-DMSO > C6F5Cl-DMSO, implying that the hydrogen-bond is stronger than the halogen-bond in the systems and, when interacting with ClC6F4H, DMSO favors the formation of a hydrogen-bond rather than a halogen-bond. Second, attractive energy dependences on 1/r(3.3) and 1/r(3.1) were established for the hydrogen-bond and halogen-bond, respectively. Third, upon the formation of a hydrogen-bond and halogen-bond, there is charge transfer from DMSO to the hydrogen-bond and halogen-bond donor. The back-group CH3 was found to contribute positively to the stabilization of the complexes. Fourth, an isosbestic point was detected in the ν(C-Cl) absorption band in the C6F5Cl-DMSO-d6 system, indicating that there exist only two dominating forms of C6F5Cl in binary mixtures; the non-complexed and halogen-bond-complexed forms. The presence of stable complexes in C6F5H-DMSO and ClC6F4H-DMSO systems are evidenced by the appearance of new peaks with fixed positions.

Comparative Study of Halogen‐ and Hydrogen‐Bond Interactions between Benzene Derivatives and Dimethyl Sulfoxide

“…Regarding the directionality of the halogen bonds, as shown in Figure 7, the optimizedC ÀBr···O and CÀI···O angles are all 1808.F or CÀCl···O angles, [18] they are 179 and 1768,w hich are very close to 1808.T his reflectst he characteristic directionality of XBs. In comparison, the optimized CÀH···O angles, as in the complexes of ClC 6 F 4 HÀDMSO and C 6 F 5 HÀDMSO, are 167 and 1638,w hichare much less than 1808 and show that HB are less directional than XB.…”

“…Ta king the molar fraction of x(C 6 F 5 X) % 0.1a sa ne xample, at this concentration, the area of the negative band in the excesss pectra of the C 6 F 5 BrÀ [D 6 ]DMSO system is barely seen, whereas that of C 6 F 5 IÀ [D 6 ]DMSO is quite pronounced. In combination with our former work, [18] 6 ]DMSO system, the negative band does not appear until am olar fraction, x(C 6 F 5 Cl), of about 0.4. This indicates that C 6 F 5 Ii samore powerful benzene derivative to break apart the DMSO self-associates, and the possible sequentialo rder of the interaction strengtho ft he five systemsi s as follows: C 6 F 5 IÀDMSO > C 6 F 5 HÀDMSO % ClC 6 F 4 HÀDMSO > C 6 F 5 BrÀDMSO > C 6 F 5 ClÀDMSO.T his conclusion is supported by the quantum chemical calculation reported in Section 2.3.1.…”

“…The OÀXs eparations demonstrate that XBs form in both cases. Based on the interaction energies shown in Figure 7a nd previous work, [18] we can easily obtain the sequential order of the interaction strength:C 6 F 5 IÀDMSO > C 6 F 5 HÀDMSO > C 6 F 5 BrÀDMSO > C 6 F 5 ClÀDMSO.T he strength of HB is between those of IÀXB and BrÀXB.…”

“…[15][16][17] In earlier work studying XB and HB between DMSO and three fluorobenzene derivatives(C 6 F 5 H, C 6 F 5 Cl, ClC 6 F 4 H), using both experimental and theoretical approaches, we found that HB was stronger than XB in these binary systemsi fc hlorine was the halogen. [18] Considering that the strength of the bromine-(BrÀXB) and iodine-based halogen bonds (IÀXB) are normally greatert han that of chlorine-based halogen bonds (ClÀXB), we extend our work to these two cases herein. 1-Bromo-2,3,4,5,6-pentafluorobenzene (C 6 F 5 Br) and1 -iodo-2,3,4,5,6-pentafluorobenzene (C 6 F 5 I) weret he selected XB donors, DMSO was still taken as the XB acceptor.…”

“…Attenuated total reflectance Fourier transform infrared (ATR-FTIR) and 19 FNMR spectroscopy and ab initio calculations were employedt oi nvestigate the halogen-bonding properties. In particular,e xcessI Rs pectroscopy [18][19][20][21][22][23][24][25][26] was used to reveal details of the molecular interactions.…”