Tziouris Petros A, Tsiafoulis Constantinos G, Vlasiou Manolis, Miras Haralampos N, Sigalas Michael P, Keramidas Anastasios D, Kabanos Themistoklis A
Section of Inorganic and Analytical Chemistry, Department of Chemistry and #NMR Center, University of Ioannina , Ioannina 45110, Greece.
Inorg Chem. 2014 Nov 3;53(21):11404-14. doi: 10.1021/ic501778d. Epub 2014 Oct 20.
Reaction of hydroxylamine hydrochloride with prop-2-enamide in dichloromethane in the presence of triethylamine resulted in the isolation of the N,N'-disubstituted hydroxylamine-(diamido) ligand, 3,3'-(hydroxyazanediyl)dipropanamide (Hhydia). The ligand Hhydia was characterized by multinuclear NMR, high-resolution electrospray ionization mass spectrometry (ESI-MS), and X-ray structure analysis. Interaction of Hhydia with trans-[Cr(III)Cl2(H2O)4]Cl·2H2O in ethanol yields the ionization isomers [Cr(III)(Hhydia)2]Cl3·2H2O(1·2H2O) and cis/trans-[Cr(III)Cl2(Hhydia)2]Cl·2H2O (2·2H2O). The X-ray structure analysis of 1 revealed that the chromium atom in Cr(III)(Hhydia)2 is bonded to two neutral tridentate O,N,O-Hhydia ligands. The twist angle, θ, in Cr(III)(Hhydia)2 is 54.5(6)(0), that is, very close to an ideal octahedron. The intramolecular hydrogen bonds developed between the N-OH group of the first ligand and the amidic oxygen atom of the second ligand and vice versa contribute to the overall stability of the cation Cr(III)(Hhydia)2. The reaction rate constant of the formation of Cr(III) complexes 1·2H2O and 2·2H2O was found to be 8.7(±0.8) × 10(-5) M(-1) s(-1) at 25 °C in methyl alcohol and follows a first-order law kinetics based on the biologically relevant ligand Hhydia. The reaction rate constant is considerably faster in comparison with the corresponding water exchange rate constant for the hydrated chromium(III). The modification of the kinetics is of fundamental importance for the chromium(III) chemistry in biological systems. Ultraviolet-visible and electron paramagnetic resonance studies, both in solution and in the solid state, ESI-MS, and conductivity measurements support the fact that, irrespective of the solvent used in the interaction of Hhydia with trans-[Cr(III)Cl2(H2O)4]Cl·2H2O, the ionization isomers[Cr(III)(Hhydia)2]Cl3·2H2O (1·2H2O) and cis/trans-[Cr(III)Cl2(Hhydia)2]Cl·2H2O (2·2H2O) are produced.The reaction medium affects only the relevant percentage of the isomers in the solid state. The thermodynamic stability of the ionization isomers 1·2H2O and cis/trans-2·2H2O, their molecular structures as well as the vibrational spectra and the energetics of the Cr(III)- Hhydia/hydia(-) were studied by means of density functional theory calculations and found to be in excellent agreement with our experimental observations.
盐酸羟胺与2-丙烯酰胺在二氯甲烷中、三乙胺存在的条件下反应，得到了N,N'-二取代的羟胺-（二酰胺）配体3,3'-（羟基偶氮二基）二丙酰胺（Hhydia）。配体Hhydia通过多核核磁共振、高分辨率电喷雾电离质谱（ESI-MS）和X射线结构分析进行了表征。Hhydia与反式-[Cr(III)Cl2(H2O)4]Cl·2H2O在乙醇中反应，生成了电离异构体[Cr(III)(Hhydia)2]Cl3·2H2O(1·2H2O)和顺式/反式-[Cr(III)Cl2(Hhydia)2]Cl·2H2O (2·2H2O)。1的X射线结构分析表明，Cr(III)(Hhydia)2中的铬原子与两个中性三齿O,N,O-Hhydia配体相连。Cr(III)(Hhydia)2中的扭转角θ为54.5(6)(0)，即非常接近理想八面体。第一个配体的N-OH基团与第二个配体的酰胺氧原子之间形成的分子内氢键，反之亦然，有助于阳离子Cr(III)(Hhydia)2的整体稳定性。在25℃的甲醇中，发现Cr(III)配合物1·2H2O和2·2H2O形成的反应速率常数为8.7(±0.8)×10(-5) M(-1) s(-1)，并且基于具有生物学相关性的配体Hhydia遵循一级动力学定律。与水合铬(III)相应的水交换速率常数相比，反应速率常数要快得多。动力学的改变对于生物系统中的铬(III)化学至关重要。紫外-可见光谱和电子顺磁共振研究，包括溶液和固态研究、ESI-MS以及电导率测量，都支持这样一个事实，即无论在Hhydia与反式-[Cr(III)Cl2(H2O)4]Cl·2H2O相互作用中使用何种溶剂，都会生成电离异构体[Cr(III)(Hhydia)2]Cl3·2H2O (1·2H2O)和顺式/反式-[Cr(III)Cl2(Hhydia)2]Cl·2H2O (2·2H2O)。反应介质仅影响固态中异构体的相关百分比。通过密度泛函理论计算研究了电离异构体1·2H2O和顺式/反式-2·2H2O的热力学稳定性、它们的分子结构以及Cr(III)-Hhydia/hydia(-)的振动光谱和能量学，发现与我们的实验观察结果非常吻合。
