Structure and wavelength modification in retinylidene iminium salts
Structure and wavelength modification in retinylidene iminium salts
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DOI：
10.1139/v96-063
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发表时间：
1996-04-01
期刊：
影响因子：
--
通讯作者：
Santarsiero, BD
中科院分区：
文献类型：
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作者：
Elia, GR;Childs, RF;Santarsiero, BD
本文研究了N-正丁基-亚视黄基亚胺的高氯酸盐和三氟甲磺酸盐2和3在溶液和固相中的光谱和结构性质。在溶液中，发现这些盐表现出非常相似的UV和NMR光谱性质。然而，在固态下，它们的吸收光谱（2，λ（max）= 504nm; 3，λ（max）= 445nm）和~（13）C NMR谱有明显的差异。用X射线晶体学测定了两种盐的晶体结构。每种盐中的阳离子都具有非常相似的构象、详细的结构和晶格中的填充。固态盐的光谱性质差异无法根据阳离子本身的任何结构差异来解释。在阳离子-阴离子相互作用方面，在每种情况下，发现N-H质子和抗衡离子的氧原子之间存在强氢键相互作用。但两种盐的N-H键含量存在显著差异。O核间距（2，N-H... O = 2.939（7）埃，在3中，2.85（1）埃）。这些结果强烈地表明，在视黄醛亚胺盐中的波长和正电荷离域是通过改变与席夫碱氮原子键合的质子和阴离子之间的距离来控制的。这里报道的工作代表了第一个例子的仲retinylideniminium盐含有N-烷基取代基，成功地通过X-射线晶体学分析。这些意见的关系，在固态的光谱性质的天然视色素进行了探讨。
The spectroscopic and structural properties of the perchlorate and triflate salts of N-n-butyl-retinylidene imine, 2 and 3, have been examined in solution and solid phases. In solution these salts were found to exhibit very similar UV and NMR spectroscopic properties. However, in the solid state marked differences in their absorption spectra (2, lambda(max) = 504 nm; 3, lambda(max) = 445 nm) and C-13 NMR spectra were found. The structures. of the two salts were determined by X-ray crystallography. The cations in each of the salts were shown to have very similar conformations, detailed structures, and packing in their crystal lattices. The differences in the spectroscopic properties of the salts in the solid state could not be accounted for on the basis of any structural differences in the cations themselves. In terms of cation-anion interactions, a strong hydrogen bonding interaction was found in each case between the N-H proton and an oxygen atom of the counterion. However, there were significant differences between the two salts in terms of the N-H ... O internuclear distances (2, N-H ... O = 2.939(7) Angstrom and in 3, 2.85(1) Angstrom). The results are strongly suggestive that the wavelength and positive charge delocalization in retinylidene iminium salts are controlled by variation of the distance between the anion and the proton bonded to the Schiff base nitrogen atom. The work reported here represents the first examples of secondary retinylidene iminium salts containing an N-alkyl substituent to be successfully analyzed by X-ray crystallography. The relationship of these observations in the solid state to the spectroscopic properties of the natural visual pigments is explored.