Structural characterization of cis-2,6-(E,E)-bis(ferrocenylidene)-N-methyl-4-piperidone and DFT evaluation of alternative polymorphic modifications via ferrocene rotation
摘要
The molecular structure of cis-2,6-(E,E)-bis(ferrocenylidene)-N-methyl-4-piperidone (1) has been determined by X-ray crystallography. Compound 1 crystallizes in the monoclinic chiral space group P2(1), a = 6.0055(17) 脜, b = 12.802(4) 脜, c = 14.465(4) 脜, 尾 = 95.438(4)掳, V = 1107.1(5) 脜3, Z = 2, and Dcalc = 1.516 Mg/m3; R = 0.0335, Rw = 0.0682 for 4230 reflections with I > 2蟽(I). The substituents at the vinyl group of each chalcone moiety exhibit a trans (entgegen) disposition, and the two ferrocene moieties adopt a syn orientation and are located on the side of the piperidone ring opposite of the nitrogen lone electron pair. Molecules of 1 pack in chains along the a axis and exhibit weak intermolecular C-H鈰疧 hydrogen bonds involving the ferrocene and carbonyl moieties of adjacent molecules. The energy difference between the ferrocene rotational isomers in 1 has been evaluated by DFT, and the lowest energy structure is represented by the solid-state structure. The barriers for the rotational isomerization of the ferrocene groups have been evaluated and are discussed in the context of polymorphic modifications available to 1.