Copper(II) Complexes of Cyclams Containing Nitrophenyl Substituents: Push–Pull Behavior and Scorpionate Coordination of the Nitro Group
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Title: | Copper(II) Complexes of Cyclams Containing Nitrophenyl Substituents: Push–Pull Behavior and Scorpionate Coordination of the Nitro Group |
Author: | Boiocchi, Massimo Ciarrocchi, Carlo Fabbrizzi, Luigi Licchelli, Maurizio Mangano, Carlo Poggi, Antonio Vázquez López, Miguel |
Affiliation: | Universidade de Santiago de Compostela. Centro de Investigación en Química Biolóxica e Materiais Moleculares Universidade de Santiago de Compostela. Departamento de Química Inorgánica |
Date of Issue: | 2015 |
Publisher: | American Chemical Society |
Citation: | Massimo Boiocchi, Carlo Ciarrocchi, Luigi Fabbrizzi, Maurizio Licchelli, Carlo Mangano, Antonio Poggi, and Miguel Vázquez López Inorganic Chemistry 2015 54 (21), 10197-10207 DOI: 10.1021/acs.inorgchem.5b01273 |
Abstract: | The three nitrophenyl–cyclam derivatives (nitrocyclams): 1-(4-nitrophenyl)-1,4,8,11-tetraazacyclotetradecane (2), 1-(2-nitrophenyl)-1,4,8,11-tetraazacyclotetradecane (3), and 1-(2,4-dinitrophenyl)-1,4,8,11-tetraazacyclotetradecane (4), in an MeCN solution, specifically incorporate the CuII ion according to an irreversible process signaled by disappearance of the yellow color for a concentration c < 1 × 10–4 M and by a yellow-to-red color change for c ≥ 1 × 10–3, and must be considered efficient and specific dosimeters of copper(II) salts. When present in the ortho position of the nitrophenyl substituent, the −NO2 group coordinates the CuII according to a scorpionate mode, while the metallocyclam system exhibits a trans-I configuration. In an MeCN solution the red trans-I-[CuII(3)]2+ and trans-I-[CuII(4)]2+ scorpionate complexes slowly convert into the violet trans-III scorpionate complexes. Kinetic aspects of the trans-I-to-trans-III configurational rearrangement were investigated in detail for the [CuII(4)]2+ system. In particular, the conversion is spectacularly accelerated by catalytic amounts of Cl–, NCO–, and F–. While for Cl– and NCO– the effect can be associated with the capability of the anion to stabilize through coordination a possible dissociative intermediate, the amazingly powerful effect of F– must be related to the preliminary deprotonation of one N–H fragment of the macrocycle, driven by the formation of the HF2– ion. Most of the metal complex species studied in solution were isolated in a crystalline form, and their molecular structures were elucidated through X-ray diffraction studies. This study documents the first examples of effective metal coordination by the nitro group |
Publisher version: | https://doi.org/10.1021/acs.inorgchem.5b01273 |
URI: | http://hdl.handle.net/10347/17020 |
DOI: | 10.1021/acs.inorgchem.5b01273 |
ISSN: | 0020-1669 |
E-ISSN: | 1520-510X |
Rights: | © 2015 American Chemical Society |
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