Kanupriya Verma, K.S.Viswanathan Department of Chemical Sciences What is different between Borazine-Acetylene and Benzene-Acetylene? A Matrix Isolation Infrared and ab initio study Kanupriya Verma, K.S.Viswanathan Email : kanupriyaverma@iisermohali.ac.in Department of Chemical Sciences Indian Institute of Science Education & Research, Mohali, Punjab-140306

Outline Introduction Matrix Isolation-The technique Experimental Details Computational Details Conclusion

Borazine-“Inorganic Benzene” Isoelectronic and isostructural analog of C6H6. Hence comparing the complexes of C6H6 and B3N3H6 is interesting. Extremely sensitive to moisture, thus posing a challenge to study this system. 1.01 Å 1.20 Å 1.43 Å Structure of B3N3H6 at MP2/aug-cc-pVDZ level.

Matrix Isolation Technique Sample + Matrix gas Vacuum chamber Substrate at low Temperature Molecules of interest are diluted with a large excess of an inert gas and the mixture then condensed onto a cold substrate. MI spectra studied using IR spectroscopy. Advantages Low temperature- only the lowest vibrational and electronic levels and possibly lowest rotational levels populated. Sharp line widths What can be studied? transient/short lived species weak non-covalent interactions molecular conformations

Computational Details Geometry Optimisation-MP2/6-311++G**&MP2/aug-cc-pVDZ Frequency Calculation-MP2/aug-cc-pVDZ AIM analysis-MP2/aug-cc-pVDZ EDA analysis-MP2/aug-cc-pVDZ

Optimised geometries of B3N3H6-C2H2 complexes at MP2/aug-cc-pVDZ π-stacked 3.41 Å -0.97 T shaped-Ac BSSE Corr.Energy(kcal/mol) 2.42 Å T shaped-NH Bent NH…C -1.65 2.43 Å 2.63 Å -1.85 -2.03

Ar matrix

π-stacked T-ac T-NH Bent NH..C

Energy Decomposition Analysis of B3N3H6-C2H2 complexes Energy (kcal/mol)

Conclusions In C6H6-C2H2, ≡C-H…π complex is the global minimum; while in B3N3H6-C2H2, a bent N-H…C complex is the global minimum. C2H2 served as the proton donor in the C6H6-C2H2 global minimum, while in B3N3H6-C2H2 global minimum, C2H2 served as the proton acceptor, thus clearly showing a switch in roles. EDA analysis showed almost equal contributions of dispersion and electrostatic energies for the global minimum in both systems. H…π for C6H6-C2H2 & Bent NH…C for B3N3H6-C2H2

Acknowledgement I thank my research supervisor Prof. K.S.Viswanathan and lab members Jyoti, Pankaj, Ginny and Dr. Anamika. I thank Dr. Sanjay Singh and Deependra Bawari for the help in synthesis of borazine. I thank MHRD and IISER Mohali, India for the research infrastructure and facilities.

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