Poderi Cecilia, Neira Iago, Franchi Paola, Mezzina Elisabetta, Baù Ilario, Neviani Paolo, Lucarini Marco
Department of Chemistry "Giacomo Ciamician", University of Bologna, Via P. Gobetti 83, 40129, Bologna, Italy.
Departamento de Química, Centro Interdisciplinar de Química y Biología (CICA), Universidade da Coruña, Facultad de Ciencias, Coruña, E-15071A, Spain.
Chemistry. 2023 Oct 2;29(55):e202301508. doi: 10.1002/chem.202301508. Epub 2023 Aug 31.
New nitroxides based on aza-crown ethers were prepared and employed as selective sensors for the detection of inorganic and organic cations by EPR analysis of the corresponding host-guest complexes. The nitroxide unit behaves as a sensitive probe for a number of alkali and alkaline earth metal cations affording EPR spectra differing in the value of nitrogen hyperfine constants and in the appearance of splitted signals due to the non-zero nuclear spin of some metal cation upon complexation. Owing to the remarkable EPR spectral differences between the host and the corresponding cation complex the new macrocycles are likely to act as multitasking tools to recognize several cationic species. EPR behaviour of the larger nitroxide azacrown 1⋅ when acting as a wheel in a radical synthetic bistable [2]rotaxane containing both secondary dialkylammonium and 1,2-bis(pyridinium) molecular stations, was also investigated. Reversible movements of the macrocycle between the two recognition sites in the rotaxane were promptly revealed by EPR, which shows significant changes either in nitrogen coupling constant values (a ) or in the spectral shape in the two rotaxane co-conformations.
基于氮杂冠醚制备了新型氮氧化物，并将其用作选择性传感器，通过对相应主客体配合物进行电子顺磁共振（EPR）分析来检测无机和有机阳离子。氮氧化物单元可作为多种碱金属和碱土金属阳离子的灵敏探针，由于某些金属阳离子在络合时具有非零核自旋，因此所提供的EPR光谱在氮超精细常数的值以及分裂信号的外观上存在差异。由于主体与相应阳离子配合物之间存在明显的EPR光谱差异，这些新型大环化合物可能会成为识别多种阳离子物种的多任务工具。还研究了较大的氮氧化物氮杂冠醚1⋅在含有仲二烷基铵和1,2 - 双（吡啶鎓）分子位点的自由基合成双稳态[2]轮烷中作为“轮子”时的EPR行为。EPR迅速揭示了大环在轮烷中两个识别位点之间的可逆移动，这在两个轮烷共构象中表现为氮耦合常数（a）值或光谱形状的显著变化。
