Fe(ii) and Co(ii) N-methylated CYCLEN complexes as paraSHIFT agents with large temperature dependent shifts†,Dalton Transactions

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Fe(ii) and Co(ii) N-methylated CYCLEN complexes as paraSHIFT agents with large temperature dependent shifts†
Dalton Transactions ( IF 3.5 ) Pub Date : 2017-12-11 00:00:00 , DOI: 10.1039/c7dt03812g
Pavel B. Tsitovich _{1,

2,

3,

4,

5} , Timothy Y. Tittiris _{1,

2,

3,

4,

5} , Jordan M. Cox _{1,

2,

3,

4,

5} , Jason B. Benedict _{1,

2,

3,

4,

5} , Janet R. Morrow _{1,

2,

3,

4,

5}

Affiliation

Several complexes of Co(II) or Fe(II) with 1,4,7,10-tetraazacyclododecane (CYCLEN) appended with 1,7-(6-methyl)2-picolyl groups are studied as ¹H NMR paraSHIFT agents (paramagnetic shift agents) for the registration of temperature. Two of the complexes, [Co(BMPC)]²⁺ and [Fe(BMPC)]²⁺, contain methyl groups only on the methyl picolyl pendents. Two other complexes, [Co(2MPC)]²⁺ and [Fe(2MPC)]²⁺, contain picolyl groups and also methyl groups on the macrocyclic amines. All macrocyclic complexes are in high spin form as shown by solution magnetic moments in the range of 5.0–5.9μ_BM and 5.3–5.8μ_BM for Co(II) and Fe(II) complexes, respectively. The ¹H NMR spectra of both of the Fe(II) complexes and one of the Co(II) complexes are consistent with a predominant diastereomeric form in deuterium oxide solutions. The highly shifted methyl proton resonances for [Co(2MPC)]²⁺ appear at 164 and −113 ppm for macrocycle and pendent picolyl methyls and show temperature coefficients of −0.58 ppm °C⁻¹ and 0.49 ppm °C⁻¹, respectively. Fe(II) complexes have less shifted methyl proton resonances and smaller temperature coefficients. The ¹H resonances of [Fe(2MPC)]²⁺ appear at 105 ppm and −46 ppm with corresponding temperature coefficients (CT) of −0.29 ppm °C⁻¹ and 0.22 ppm °C⁻¹, respectively. The relatively narrow linewidths of [Fe(2MPC)]²⁺, however, produce superior CT/FWHM values of 0.44 and 0.31 °C⁻¹ for the N-methyl and picolyl proton resonances where FWHM is the full width at half maximum of the ¹H resonance. The crystal structure of [Co(BMPC)]Cl₂ shows a six-coordinate Co(II) bound to the macrocyclic amines and two pendent picolyl groups. The distorted trigonal prismatic geometry of the complex resembles that of an analogous complex containing four 6-methyl-2-picolyl groups, in which only two picolyl pendents are coordinated.

中文翻译：

Fe（ii）和Co（ii）N-甲基化CYCLEN配合物作为paraSHIFT剂，具有较大的温度依赖性位移†

研究了Co（II）或Fe（II）与1,4,7,10-四氮杂环十二烷（CYCLEN）附加了1,7-（6-甲基）2-甲基吡啶基的几种配合物，作为¹ H NMR paraSHIFT剂（顺磁性移位剂）用于温度记录。两种配合物[Co（BMPC）] ²⁺和[Fe（BMPC）] ²⁺仅在甲基甲基吡啶基侧基上含有甲基。[Co（2MPC）] ²⁺和[Fe（2MPC）] ^2+这两个其他配合物在大环胺上还含有甲基吡啶基和甲基。所有大环配合物是在高自旋形式如在5.0-5.9的范围内所示的解决方案的磁矩μ _BM和5.3-5.8 μ _BM分别用于Co（II）和Fe（II）配合物。Fe（II）配合物和Co（II）配合物之一的¹ H NMR谱图与氘氧化溶液中的主要非对映异构体形式一致。[Co（2MPC）] ²⁺的高位移甲基质子共振出现在大环和悬垂的甲基吡啶甲基上，分别为164和-113 ppm，并且显示的温度系数分别为-0.58 ppm°C ^-1和0.49 ppm°C ^-1。Fe（II）配合物具有较少的移位的甲基质子共振和较小的温度系数。[Fe（2MPC）] ²⁺的¹ H共振出现在105 ppm和-46 ppm时，相应的温度系数（CT）分别为-0.29 ppm°C ^-1和0.22 ppm°C ^-1。然而，[Fe（2MPC）] ²⁺的相对较窄的线宽对于N-甲基和甲基吡啶质子共振产生了更好的CT / FWHM值，分别为0.44和0.31°C ^-1，其中FWHM是半峰全宽。¹ H共振。[Co（BMPC）] Cl ₂的晶体结构显示六坐标的Co（II）结合到大环胺和两个悬垂的甲基吡啶基上。该配合物的扭曲的三角棱柱形几何形状类似于含有四个6-甲基-2-吡啶甲基的类似配合物的几何形状，其中仅两个吡啶甲基悬垂配位。

更新日期：2017-12-11

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