Spectral analysis and crystal structure of two substituted spiro acenaphthene structures

The crystal structure of spiro[2.2"]acenaphthene-1"-onespiro[3.3']-5'-(2-bromophenylmethylidene)-1'-methylpiperidin-4'-one-4-(2-bromophenyl)octahydroindolizine (Ia) and spiro[2.2"]acenaphthene-1"-onespiro[3.3']-5'-(4-bromophenylmethylidene)-1'-methylpiperidin-4'-one-4-(4-bromophenyl)octahydroindolizine (Ib) were elucidated by single crystal X ray diffraction. Compound (Ia), C37H32Br2N2O2, crystallizes in the Orthorombic system, space group P212121 with a = 9.6989(5) , b = 16.3615(9) , c = 19.8997(11) and Z = 4. Compound (Ib), having the same molecular formula, crystallizes in the monoclinic system, space group P 21/n with a = 8.3169(5) , b = 16.9397(9) , c= 22.2466(13) , β = 96.943(3)° and Z = 4. The central piperidine ring adopts twisted conformation, the piperidine of octahydroindolizine ring is in half chair conformation and the pyrrole ring is in twisted envelope conformation in both the compounds (Ia) and (Ib). Details of the preparation, NMR and crystal structure determination and intra- and inter- molecular interactions of the compounds are given.