The new compound [Li(NO3)(phen)](n) (phen: 1,10-phenanthroline) has been synthesized and characterized by elemental analysis, and single crystal X-ray diffraction. The Li+ ion is five coordinated occupied distorted TBP (trigonal bipyramidal) geometry. The Li+ ions are bridged by nitrate anions into 1D polymeric chain. The nitrate anions are coordinated to Li+ ions through chelating and bridging bidentate mode of binding. There are cooperative noncovalent interactions like strong or weak H-bonding, weak and CH interactions are involved to form 2D network. Thermal properties of this complex have been completely described by thermo gravimetric analysis (TGA). Both molecular and crystal structures of this compound were compared and discussed the intermolecular interactions by using Hirshfeld surface analysis and 2D-fingerprint plots. The optimized molecular geometry by DFT calculations agrees closely with obtained from the crystallographic study. Hirshfeld surface analysis of compound (I) indicates that HH, and CH contacts can account for 30.9, 15.0 and 7.4% respectively of the total Hirshfeld surface area.