The Non-covalent Bonding Nature Of The S Chalcogen Bond

The S chalcogen bonds play an important role in different fields such as materials science,pharmaceutical chemistry,crystal engineering and biological sciences.However,scarce information is available on the bonding mechanisms and nature of the S chalcogen bond,which requires a systematic and indepth study.In this dissertation,Fourier transform microwave spectroscopy,which has obvious advantages in the determination of molecular structure,non-covalent interactions and internal dynamics,was used to investigated the the chalcogen-bonded complexes formed by two representative chalcogen bond donors,SO₂ and C₂F₄S₂,with different chalcogen bond acceptors,combined with quantum chemical calculations.The main researches are classified as follows:The instrument structure and working principle of the high resolution supersonic-jet Fourier transform microwave spectrometer and the chirped-pulsed broadband microwave spectrometer used in this dissertation are briefly introduced in the chapter?.In the chapter ? and ?,the bonding nature of S···O chalcogen bond are reported.Two representative chalcogen bond donors,SO₂ and C₂F₄S₂,were selected to explore the effects of the different chalcogen bond donor on the bongding nature of S chalcogen bond.The rotational spectra of SO₂···cyclohexanol and C₂F₄S₂···H₂O complexes were measured and assigned in chapter?and?,respectively.By using the experimental rotational constants,the molecular structures can be obtained.Natural Bond Orbital and Symmetry-adapted perturbation theory analyses were performed to evaluate the strength and explore the nature of chalcogen bonds.By comparing investigations of the two complexes,it is possible to explore the similarities and differences of the S chalcogen bond formed by SO₂(?-hole)or C₂F₄S₂(?-hole).In the chapter ? and ?,the bonding nature of S···N and S···S chalcogen bonds are investigated,which are compared with that of S···O chalcogen bond to explore the effects of different chalcogen bond acceptors on the strength and bonding characteristics of S chalcogen bond.The rotational spectra of C₂F₄S₂···isopropylamine and C₂F₄S₂···H₂S complex were measured and assigned in chapter?and?,respectively.By using the least square fitting procedure,the structural parameters connected with the chalcogen bond can be obtained through the experimental rotational constants.The strength of chalcogen bond and the importance of electrostatics,induction,dispersion and exchange repulsion in intermolecular interactions were evaluated by performing Natural Bond Orbital and Symmetry-adapted perturbation theory analyses.The investigations of C₂F₄S₂···isopropylamine and C₂F₄S₂···H₂S complexes were compared with that of C₂F₄S₂···H₂O complex to compare the strength and bonding nature of S···O,S···N and S···S chalcogen bonds.In the chapter ?,the bonding nature of S···?chalcogen bond are investigated,which are compared with that of S···n chalcogen bond.The rotational spectrum of SO₂···benzofuran complex was measured and assigned.By using the least square fitting procedure,the molecular structure of SO₂···benzofuran complex can be obtained through the rotational constants.Natural Bond Orbital and Symmetry-adapted perturbation theory analyses were carried out.The results were compared with those of SO₂···cyclohexanol,C₂F₄S₂···H₂O,C₂F₄S₂···isopropylamine and C₂F₄S₂···H₂S complexes to explore the similarities and differences in the bonding characteristics and mechanism of S···n and S···?chalcogen bond.