title: Nitration of Norcorrolatonickel(II): First Observation of a Diatropic Current in a System Comprising a Norcorrole Ring.
abstract: A one-pot reaction of 5,14-bis(mesityl)-norcorrolatonickel(II) with isoamyl nitrite under mild reaction conditions resulted in the consecutive formation of 3-nitro-, 3,12-dinitro- and 3,16-dinitro-, 3,7,12-trinitro-, and 3,7,12,16-tetranitro-norcorrolatonickel(II) in 50-80% yield. The substituted macrocycles retained their antiaromatic character. The observed regioselectivity of the substitution was analyzed by comparing the relative energies of the DFT energy-optimized models of the radical or arenium cationic intermediates that can be formed upon reaction with NO2. The nitrated systems were characterized by high-resolution mass spectrometry, NMR and UV/Vis spectroscopy, X-ray diffraction analysis, cyclic voltammetry, and DFT calculations. A significant and systematic cathodic shift of the redox couples was observed to correlate with an increasing number of the NO2 group. A decrease of the LUMO energies in the tri- and tetra-nitrated products stabilizes mono- and bis-reduced complexes of these ligands. The reduction takes place on the macrocycle rather than on the metal ion leading to the consecutive formation of stable paramagnetic monoanion radicals and water-soluble diamagnetic dianions with an aromatic character, which were revealed by ESR and (1)H NMR measurements, respectively. The electronic structures of the reduced forms were analyzed by extensive TD-DFT calculations.
authors.affiliation: Key Laboratory of Theoretical Organic Chemistry and Functional Molecules, Ministry of Education, School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan, Hunan, 411201, China.
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Deng
authors.affiliation: Key Laboratory of Theoretical Organic Chemistry and Functional Molecules, Ministry of Education, School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan, Hunan, 411201, China. lixiaofang@iccas.ac.cn.
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Chemistry, University of Wrocław, F. Joliot-Curie 14, 50383, Wrocław, Poland.
authors.forename: Marcin
authors.initials: M
authors.lastname: Stępień
authors.affiliation: Department of Chemistry, University of Wrocław, F. Joliot-Curie 14, 50383, Wrocław, Poland. piotr.chmielewski@chem.uni.wroc.pl.
authors.forename: Piotr J
authors.initials: PJ
authors.lastname: Chmielewski
keywords: nickel; nitration; norcorroles; porphyrinoids; reduction