The structural, spectral (FT-IR, Raman, H-1 and (13) C NMR chemical shift and UV-Vis. spectroscopies) and electronic properties for bromido(eta(6)-1-isopropyl-4-methylbenzene )(7-oxocyclo hepta-1,3,5-trien-1-olato-kappa O-2,O')osmium(II) were investigated using experimental and theoretical methods. The bond parameters and aromatic pi-pi stacking interactions in molecular structure of the half-sandwich organometallic Os(II)-arene complex under investigation were studied. Hirshfeld surface analysis was used to assess C-H center dot center dot center dot O and C-H center dot center dot center dot Br intermolecular interactions in the crystal packing. To support experimental vibrational wavenumbers, structural parameters, NMR chemical shifts and electronic absorption spectroscopic data, theoretical computations were performed with Density functional theory (DFT) using the B3LYP method with a double-zeta valence basis set (LanL2DZ). DFT was also applied to explore the HOMO, LUMO, MEP, NBO and NLO of the Os(II) complex compound at the mentioned computational level. Good agreement was found between the calculated results and experimental data. (C) 2019 Elsevier B.V. All rights reserved.