Boiocchi Massimo, Ciarrocchi Carlo, Fabbrizzi Luigi, Licchelli Maurizio, Mangano Carlo, Poggi Antonio, Vázquez López Miguel
Centro Singular de Investigación en Química Biolóxica e Materiales Moleculares (CIQUS) and Departamento de Química Inorgánica, Universidade de Santiago de Compostela , 15782 Santiago de Compostela, Spain.
Inorg Chem. 2015 Nov 2;54(21):10197-207. doi: 10.1021/acs.inorgchem.5b01273. Epub 2015 Oct 15.
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 Cu(II) 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 Cu(II) according to a scorpionate mode, while the metallocyclam system exhibits a trans-I configuration. In an MeCN solution the red trans-I-Cu(II)(3) and trans-I-Cu(II)(4) 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 Cu(II)(4) 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.
三种硝基苯基环胺衍生物（硝基环胺）：1-(4-硝基苯基)-1,4,8,11-四氮杂环十四烷（2）、1-(2-硝基苯基)-1,4,8,11-四氮杂环十四烷（3）和1-(2,4-二硝基苯基)-1,4,8,11-四氮杂环十四烷（4），在乙腈溶液中，对于浓度c < 1×10⁻⁴ M时，通过黄色消失这一不可逆过程特异性地结合Cu(II)离子，而对于c≥1×10⁻³时，则通过黄色到红色的颜色变化来结合，并且必须被视为铜(II)盐的高效且特异性剂量计。当硝基苯基取代基处于邻位时，-NO₂基团以螯合模式与Cu(II)配位，而金属环胺体系呈现反式-I构型。在乙腈溶液中，红色的反式-I-[Cu(II)(3)]²⁺和反式-I-[Cu(II)(4)]²⁺螯合配合物会缓慢转化为紫色的反式-III螯合配合物。针对[Cu(II)(4)]²⁺体系详细研究了反式-I到反式-III构型重排的动力学方面。特别地，催化量的Cl⁻、NCO⁻和F⁻能显著加速这种转化。虽然对于Cl⁻和NCO⁻，这种效应可归因于阴离子通过配位稳定可能的解离中间体的能力，但F⁻令人惊讶的强大效应必定与大环中一个N-H片段的初步去质子化有关，这是由HF₂⁻离子的形成驱动的。溶液中研究的大多数金属配合物物种都以晶体形式分离出来，并且通过X射线衍射研究阐明了它们的分子结构。这项研究记录了硝基有效金属配位的首个实例。
