Structure-property relationship of 3-(4-substituted benzyl)-1,3-diazaspiro[4.4]nonane-2,4-diones as new potentional anticonvulsant agents. An experimental and theoretical study

The structure-property relationship of newly synthesized 3-(4-substituted benzyl)-1,3-diazaspiro [4.4] nonane-2,4-diones was studied by experimental and calculated methods. The prepared compounds were characterized by UV-Vis, FT-IR, H-1 NMR and C-13 NMR spectroscopy and elemental analysis. The crystal structure was elucidated by single-crystal X-ray diffraction. The 3-benzy1-1,3-diazaspiro[4.41nonane-2,4-dione crystallizes in triclinic P-1 space group, with two crystallographically independent molecules in the asymmetric unit. Cyclopentane ring adopts an envelope conformation. A three-dimensional crystal packing is governed by hydrogen N-H center dot center dot center dot O bonds, numerous C-H center dot center dot center dot O/N and C-H center dot center dot center dot pi interactions between neighboring molecules. Density functional theory (DFT) calculations with B3LYP and M06-2X methods using 6-311++G(d,p) basis set were performed to provide structural and spectroscopic information. Comparisons between experimental and calculated UV-Vis spectral properties suggest that the monomeric form of the investigated spirohydantoins is dominant in all used solvents. The effects of substituents on the absorption spectra of spirohydantoins are interpreted by correlation of absorption frequencies with Hammett equation. The lipophilicities of the investigated molecules were estimated by calculation of their log P values. Some of the spirohydantoins synthesized in this work, exhibit the lipophilicities comparable to the standard medicine anticonvulsant drug Phenytoin. The results obtained in this investigation afford guidelines for the preparation of new derivatives of spirohydantoin as potential anticonvulsant agents and for better understanding the structure-activity relationship.