Growth, Quantum Chemical Computations, NLO and Spectroscopic Studies of 2-Amino 5- Chloro Pyridine Single Crystal in Comparison with Certain Aminopyridine Derivatives.

Single crystals of an organic 2-amino 5-chloropyridine (2A5CP) have been grown by slow evaporation and confirmed by XRD. DFT calculations, spectroscopic studies, Photoluminescence, and thermal analysis were performed to characterize the crystal. The third-order nonlinearity was measured using the open and closed aperture Z-scan techniques. The most stable molecular structure is optimized by DFT/CAM-B3LYP method with 6-311++G(d,p) basis set in the Gaussian 09 program package. Optimized geometry, AIM analysis, MEP, and Mulliken Population analysis prove the presence of intermolecular N-H…N hydrogen bonds in the dimer. Natural Bond Orbital analysis predicts that the chlorine and NH2 substitutions induce hyperconjugation with σ bonds in the C-C double bond and strong π conjugation in the pyridine ring. The π*→ π* conjugative intramolecular charge-transfer interactions in 2A5CP have stabilization energy ∼ 984 kJ/mol which leads to enhancing optical properties. Experimental NMR, FTIR and FT-Raman spectra of 2A5CP have been recorded and compared with theoretical spectra. The vibrational wavenumbers are simulated (scaled) and assigned based on potential energy distribution. Hirshfeld surface analysis represented in a 2D fingerprint plot displays the percentage contribution of interactions between atoms. The optical bandgap of the grown crystal has been calculated as 3.54 eV. In the present investigation, the percentage contribution of interactions, intermolecular hydrogen-bonded interactions, charge on N and H atoms, HOMO-LUMO energy gap, electronic transitions, first-order hyperpolarizability, and two-photon absorption coefficient (β) of 2A5CP were compared with those of certain aminopyridine derivatives. The results of our investigation predict that the 2A5CP is a stable complex below 147 °C with third-order nonlinearity that can be used as a new green-light emitting organic material with potential application as an efficient optical limiter in optoelectronics.