1. INDIAN INSTITUTE OF SCIENCE EDUCATION AND RESEARCH (IISER) MOHALI
H-π beats n-σ in Phenylacetylene-HCl Hydrogen Bonded Heterodimer: A Matrix Isolation Infrared and Ab Initio Study
Ginny Karir, K.S.Viswanathan
IN PURSUIT OF KNOWLEDGE
INDIAN INSTITUTE OF SCIENCE EDUCATION AND RESEARCH (IISER) MOHALI
Knowledge city, Sector 81, Ajitgarh, Manauli P.O , Punjab, India. 

2. Outline Motivation Matrix Isolation Phenylacetylene-HCl Complexes
Experimental and Computational Details
Conclusions

3. Motivation – The n-σ vs H-π competition
n-σ complex
H-π complex
Not Possible ? +  
Can we force H-π structure to be seen ?
Matrix
Matrix
Matrix
IR UV double resonance
Matrix
Molecular Beam
Phenylacetylene-MeOH
Phenylacetylene-Diethyl Ether
Phenylacetylene-HCl
Phenylacetylene-H2O

4. What does Matrix Isolation do ?
Matrix species
Sample molecule

5. Experimental Setup Matrix Isolation Setup E G C D F B A A- Cryostat
B- Diffusion Pump
C- FT-IR
D- Mixing Chamber
E- Data Acquisition
F- Sample Container
G-Inert Gas Cylinder A E G C D F B
Matrix Isolation Setup

6. Phenylacetylene-HCl Complexes
MP2/aug-cc-pVDZ
Calculations performed at other levels of theory like
M06-2X ,MP2,CCSD (single point) using G** and aug-cc-pVDZ basis sets confirm the same energy ordering
2.71 Å
n-σ
(-0.91 kcal/mol)
H-π phenyl
2.41 Å
(-3.80 kcal/mol)
2.30 Å
2.37 Å
H-π acetylene
(-3.81 kcal/mol)
Note : BSSE corrected energy in kcal/mol is given in parenthesis

8. AIM Calculation at M2/aug-cc-pVDZ
Electron density at BCP for Phenylacetylene-HCl H-π complex is greater than n-σ complex.
Complex
ρ (rc) a.u.
1 (H-π acetylene)
0.0165
2 (H-π phenyl)
0.0129
3 (n-σ)
0.0084

9. NBO and EDA Analysis Natural BondOrbital Analysis
Major Interaction in the observed H-π complex is between the bonding orbital of C≡C to antibonding orbital of H-Cl.
Energy Decomposition Analysis
Dispersion component dominates in H-π complex
Electrostatic component dominant interaction in n-σ complexes.

10. Conclusions
H-π complexes were observed experimentally in matrix , hence only H- π beats n-σ complex in phenylacetylene-HCl complex.
H-π phenyl Complex
2.41 Å
2.30 Å
2.37 Å
H-π acetylene Complex

11. Acknowledgements
My sincere gratitude to my Research supervisor Prof. K.S. Viswanathan.
Thanks to my lab members Pankaj Dubey, Jyoti Saini , Kanupriya Verma and Dr. Anamika .
Finally thanks to MHRD for funding and IISER-Mohali for providing the necessary facilities .