Chetcuti Michael J, Naghmouchi Haithem, Hamdi Abdelwaheb, Karmazin Lydia
Organometallic Chemistry Group, LIMA-UMR CNRS 7042, European School of Chemistry, Polymers and Materials (ECPM), Universities of Strasbourg and of Upper Alsace, 25 Rue Becquerel, 67087 Strasbourg, France.
Department of Chemistry, College of Sciences and Arts in Ar Rass, Qassim University, Buraydah 52222, Saudi Arabia.
Molecules. 2023 Jul 27;28(15):5697. doi: 10.3390/molecules28155697.
A series of cationic p-tert-butylcalix[4]arenes, with side-arms that are functionalized with imidazolium groups, have been synthesized in good yields. The parent tetrahydroxy para-t-butyl-calix[4]arene was dialkylated at the phenolic hydrogen atoms using α,ω-dibromo-alkanes to yield bis(mono-brominated) alkoxy-chains of variable length. The brominated side-arms in these compounds were then further alkylated with substituted imidazoles (N-methylimidazole, N-(2,4,6-trimethyl-phenyl)imidazole, or N-(2,6-di-isopropylphenyl)imidazole) to yield a series of dicationic calixarenes with two imidazolium groups tethered, via different numbers of methylene spacers ( = 2-4), to the calixarene moiety. Related tetracationic compounds, which contain four imidazolium units linked to the calix[4]arene backbone, were also prepared. In all of these compounds, the NMR data show that the calixarenes adopted a cone configuration. All molecules were characterized by NMR spectroscopy and by MS studies. Single crystal X-ray diffraction studies were attempted on many mono-crystals of these cations, but significant disorder problems, partly caused by occluded solvent in the lattice, and lack of crystallinity resulting from partial solvent loss, precluded the good resolution of most X-ray structures. Eventually, good structural data were obtained from an unusually disordered single crystal of , (1,3)-Cone-5,11,17,23---butyl-25,27-di-hydroxy-26,28--[2-(N-2,6-diisopropylphenyl-imidazolium)ethoxy]calix[4]arene dibromide and its presumed structure was confirmed. The structure revealed the presence of H-bonded interactions and some evidence of π-stacking. Some of these imidazolium salts were reacted with nickelocene to form the nickel -heterocyclic carbene (NHC) complexes -. A bis-carbene nickel complex was also isolated and its structure was established by single crystal X-ray diffraction studies. The structure was disordered and not of high quality, but the structural data corroborated the spectroscopic data.
一系列带有咪唑鎓基团官能化侧链的阳离子对叔丁基杯[4]芳烃已被高收率合成。母体四羟基对叔丁基杯[4]芳烃在酚羟基氢原子处使用α,ω-二溴代烷烃进行二烷基化反应，得到不同长度的双（单溴代）烷氧基链。然后这些化合物中的溴化侧链再与取代咪唑（N-甲基咪唑、N-(2,4,6-三甲基苯基)咪唑或N-(2,6-二异丙基苯基)咪唑）进一步烷基化，得到一系列带有两个通过不同数量的亚甲基间隔基（= 2 - 4）连接到杯芳烃部分的咪唑鎓基团的双阳离子杯芳烃。还制备了相关的含有四个连接到杯[4]芳烃主链的咪唑鎓单元的四阳离子化合物。在所有这些化合物中，核磁共振数据表明杯芳烃呈现锥形构型。所有分子均通过核磁共振光谱和质谱研究进行了表征。对这些阳离子的许多单晶尝试进行单晶X射线衍射研究，但部分由于晶格中包藏溶剂导致的严重无序问题以及部分溶剂损失导致的结晶度不足，使得大多数X射线结构无法得到良好解析。最终，从一种异常无序的单晶（1,3）-锥-5,11,17,23-四叔丁基-25,27-二羟基-26,28-二-[2-(N-2,6-二异丙基苯基-咪唑鎓)乙氧基]杯[4]芳烃二溴化物中获得了良好的结构数据，并证实了其推测结构。该结构揭示了氢键相互作用以及一些π-堆积的证据。其中一些咪唑鎓盐与二茂镍反应形成镍-杂环卡宾（NHC）配合物。还分离得到了一种双卡宾镍配合物，并通过单晶X射线衍射研究确定了其结构。该结构无序且质量不高，但结构数据证实了光谱数据。
