Planochromism of cyanoxime anions: computational and mechanistic studies in solid state and solutions.
Planochromism of cyanoxime anions: computational and mechanistic studies in solid state and solutions.
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氰肟阴离子的平面变色：固态和溶液中的计算和机械研究。
DOI：
10.1016/j.ica.2020.119570
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发表时间：
2020
影响因子：
2.8
通讯作者：
Gerasimchuk,Nikolay
中科院分区：
文献类型：
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作者：
Morton,Jeffrey;Dennison,Richard;Nemykin,Victor;Gerasimchuk,Nikolay
苯甲酰基氰基肟NC-C（双键N-OH）-C（O）-C6 H5（后来的H（BCO））是一种新型的两性多齿配体，由于其配位化合物具有良好的生物活性而受到人们的关注。无色H（BCO）在去质子化后，通常会获得取决于抗衡阳离子和系统的颜色。合成了五种H（BCO）与无色有机和无机单阳离子Cs、Tl、Ag、N（CH_3）_4和As（C_6 H_5）_4的衍生物，并通过X射线衍射、振动光谱和电子光谱进行了表征。化合物在固态和溶液中表现出意想不到的和显著的颜色差异，这是具有挑战性的解释，从而避免了详细的研究，包括高水平的DFT/TDFT计算。研究发现，BCO−阴离子在极性质子ROH（R双键H、CH 3、C2 H5、C3 H7、C4 H9）溶剂中表现出负的溶剂化变色，并呈现黄色，如四烷基铵或碱金属盐。在极性非质子溶剂如CH 3CN、DMF和DMSO中，BCO-阴离子的溶液是红色的。颜色来源于阴离子的n → π * 跃迁。固态结构证明了BCO−阴离子的平面性与其颜色以及C单键N单键O片段中的键合特征的相当大的依赖性：黄色与anoxime相关（键长C单键N比N单键O短），而红色是由于亚硝基特征（键长C单键N比N单键O长）。向含BCO的盐的红色溶液中加入乙醇导致颜色变为黄色，这是氰基肟的C单键N单键O片段和溶剂之间形成H-键的结果，也导致结构的平坦化。基于实验证据和TD/DFT计算，对这种新的变色效应给出了解释。
The benzoylcyanoxime, NC-C(double bondN-OH)-C(O)-C6H5(later H(BCO)), represents a new ampolydentate ligand that received attention in the light of useful biological properties of its coordination compounds. Colorless H(BCO), upon deprotonation, gains color that depends on the counter-cation and the system in general. Five derivatives of H(BCO), with colorless organic and inorganic mono-cations – Cs, Tl, Ag, N(CH3)4and As(C6H5)4– were synthesized and characterized by the X-ray analysis, vibrational and electronic spectroscopy. Compounds exhibited unexpected and significant differences in color, both in solid state and in solutions, that were challenging to explain, thereby warranting detailed investigation including high-level DFT/TDFT computations. It was found that the BCO−anion demonstrates negative solvatochromic in polar protic ROH (Rdouble bondH, CH3, C2H5, C3H7, C4H9) solvents, and appears yellow in color, as tetraalkylammonium or alkali metal salts. In polar aprotic solvents, such as CH3CN, DMF, and DMSO, solutions of the BCO-anion are red. The color originates fromn→ π * transition in the anion. Solid state structures evidenced a considerable dependence on planarity of the BCO−anion on its color, as well as on the character of bonding in the Csingle bondNsingle bondO fragment: yellow color is associated with anoxime(bond length Csingle bondN is shorter than Nsingle bondO), while red color is due to thenitrosocharacter (bond length Csingle bondN is longer than the Nsingle bondO). An addition of ethanol to red solutions of the BCO-containing salts leads to the color change to yellow, which is the result of the formation of an H-bond between the Csingle bondNsingle bondO fragment of cyanoxime and the solvent, also leading to the flattening of the structure. An explanation for this new color-changing effect was offered, based on experimental evidence and TD/DFT calculations.