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Understanding the Coordination Modes of [Cu(acac)2(imidazole)n=1,2] Adducts by EPR, ENDOR, HYSCORE, and DFT Analysis
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2017-09-21 00:00:00 , DOI: 10.1021/acs.inorgchem.7b01874 Nadine Ritterskamp 1 , Katherine Sharples 1 , Emma Richards 1 , Andrea Folli 1 , Mario Chiesa 2 , James A. Platts 1 , Damien M. Murphy 1
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2017-09-21 00:00:00 , DOI: 10.1021/acs.inorgchem.7b01874 Nadine Ritterskamp 1 , Katherine Sharples 1 , Emma Richards 1 , Andrea Folli 1 , Mario Chiesa 2 , James A. Platts 1 , Damien M. Murphy 1
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The interaction of imidazole with a [Cu(acac)2] complex was studied using electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), hyperfine sublevel correlation spectroscopy (HYSCORE), and density functional theory (DFT). At low Im ratios (Cu:Im 1:10), a 5-coordinate [Cu(acac)2Imn=1] monoadduct is formed in frozen solution with the spin Hamiltonian parameters g1 = 2.063, g2 = 2.063, g3 = 2.307, A1 = 26, A2 = 15, and A3 = 472 MHz with Im coordinating along the axial direction. At higher Im concentrations (Cu:Im 1:50), a 6-coordinate [Cu(acac)2Imn=2] bis-adduct is formed with the spin Hamiltonian parameters g1 = 2.059, g2 = 2.059, g3 = 2.288, A1 = 30, A2 = 30, and A3 = 498 MHz with a poorly resolved 14N superhyperfine pattern. The isotropic EPR spectra revealed a distribution of species ([Cu(acac)2], [Cu(acac)2Imn=1], and [Cu(acac)2Imn=2]) at Cu:Im ratios of 1:0, 1:10, and 1:50. The superhyperfine pattern originates from two strongly coordinating N3 imino nitrogens of the Im ring. Angular selective 14N ENDOR analysis revealed the NA tensor of [34.8, 43.5, 34.0] MHz, with e2qQ/h = 2.2 MHz and η = 0.2 for N3. The hyperfine and quadrupole values for the remote N1 amine nitrogens (from HYSCORE) were found to be [1.5, 1.4, 2.5] MHz with e2qQ/h = 1.4 MHz and η = 0.9. 1H ENDOR also revealed three sets of HA tensors corresponding to the nearly equivalent H2/H4 protons in addition to the H5 and H1 protons of the Im ring. The spin Hamiltonian parameters for the geometry optimized structures of [Cu(acac)2Imn=2], including cis-mixed plane, trans-axial, and trans-equatorial, were calculated. The best agreement between theory and experiment indicated the preferred coordination is trans-equatorial [Cu(acac)2Imn=2]. A number of other Im derivatives were also investigated. 4(5)-methyl-imidazole forms a [Cu(acac)2(Im-3)n=2] trans-equatorial adduct, whereas the bulkier 2-methyl-imidazole (Im-2) and benzimidazole (Im-4) form the [Cu(acac)2(Im-2,4)n=1] monoadduct only. Our data therefore show that subtle changes in the substrate structure lead to controllable changes in coordination behavior, which could in turn lead to rational design of complexes for use in catalysis, imaging, and medicine.
中文翻译：
通过EPR，ENDOR，HYSCORE和DFT分析了解[Cu（acac）2（咪唑）n = 1,2 ]加合物的配位模式
使用电子顺磁共振（EPR），电子核双共振（ENDOR），超精细次相关光谱（HYSCORE）和密度泛函理论（DFT）研究了咪唑与[Cu（acac）2 ]配合物的相互作用。在低Im比率下（Cu：Im 1:10），在具有自旋哈密顿参数g 1 = 2.063，g 2 = 2.063，g的冰冻溶液中形成5配位[Cu（acac）2 Im n = 1 ]单加合物。3 = 2.307，A 1 = 26，A 2 = 15和A 3= 472 MHz，Im沿轴向协调。在较高的Im浓度下（Cu：Im 1:50），形成了具有自旋哈密顿参数g 1 = 2.059，g 2 = 2.059，g 3的6坐标[Cu（acac）2 Im n = 2 ]双加合物。= 2.288，A 1 = 30，A 2 = 30和A 3 = 498 MHz，且分辨出的14 N超超精细图谱较差。各向同性的EPR光谱揭示了物种（[Cu（acac）2 ]，[Cu（acac）2 Im n = 1 ]和[Cu（acac）2 Im n = 2 ]）时，Cu：Im的比例为1：0、1：10和1:50。超超细图形来自Im环的两个强烈配位的N 3亚氨基氮。角度选择性14 N ENDOR分析显示[ 34.8，43.5，34.0 ] MHz的N A张量，其中e 3 qQ / h = 2.2 MHz，N 3的η= 0.2 。发现远程N 1胺氮（来自HYSCORE）的超精细和四极值为[1.5、1.4、2.5] MHz，e 2 qQ / h = 1.4 MHz，η= 0.9。1 H ENDOR还透露了三组H除了Im环的H 5和H 1质子外，还对应于几乎相等的H 2 / H 4质子的张量。计算了[Cu（acac）2 Im n = 2 ]的几何优化结构的自旋哈密顿量参数，包括顺式混合平面，反轴式和反赤道式。理论和实验之间的最佳协议指出的优选的协调是反式-equatorial [铜（ACAC）2林Ñ = 2]。还研究了许多其他的Im衍生物。4（5）-甲基咪唑形成[Cu（acac）2（Im- 3）n = 2 ]反赤道加合物，而较大的2-甲基咪唑（Im- 2）和苯并咪唑（Im- 4）仅形成[Cu（acac）2（Im- 2,4）n = 1 ]单加合物。因此，我们的数据表明，底物结构的细微变化导致配位行为的可控变化，进而可以合理设计用于催化，成像和医学的复合物。
更新日期：2017-09-21
中文翻译：
通过EPR，ENDOR，HYSCORE和DFT分析了解[Cu（acac）2（咪唑）n = 1,2 ]加合物的配位模式
使用电子顺磁共振（EPR），电子核双共振（ENDOR），超精细次相关光谱（HYSCORE）和密度泛函理论（DFT）研究了咪唑与[Cu（acac）2 ]配合物的相互作用。在低Im比率下（Cu：Im 1:10），在具有自旋哈密顿参数g 1 = 2.063，g 2 = 2.063，g的冰冻溶液中形成5配位[Cu（acac）2 Im n = 1 ]单加合物。3 = 2.307，A 1 = 26，A 2 = 15和A 3= 472 MHz，Im沿轴向协调。在较高的Im浓度下（Cu：Im 1:50），形成了具有自旋哈密顿参数g 1 = 2.059，g 2 = 2.059，g 3的6坐标[Cu（acac）2 Im n = 2 ]双加合物。= 2.288，A 1 = 30，A 2 = 30和A 3 = 498 MHz，且分辨出的14 N超超精细图谱较差。各向同性的EPR光谱揭示了物种（[Cu（acac）2 ]，[Cu（acac）2 Im n = 1 ]和[Cu（acac）2 Im n = 2 ]）时，Cu：Im的比例为1：0、1：10和1:50。超超细图形来自Im环的两个强烈配位的N 3亚氨基氮。角度选择性14 N ENDOR分析显示[ 34.8，43.5，34.0 ] MHz的N A张量，其中e 3 qQ / h = 2.2 MHz，N 3的η= 0.2 。发现远程N 1胺氮（来自HYSCORE）的超精细和四极值为[1.5、1.4、2.5] MHz，e 2 qQ / h = 1.4 MHz，η= 0.9。1 H ENDOR还透露了三组H除了Im环的H 5和H 1质子外，还对应于几乎相等的H 2 / H 4质子的张量。计算了[Cu（acac）2 Im n = 2 ]的几何优化结构的自旋哈密顿量参数，包括顺式混合平面，反轴式和反赤道式。理论和实验之间的最佳协议指出的优选的协调是反式-equatorial [铜（ACAC）2林Ñ = 2]。还研究了许多其他的Im衍生物。4（5）-甲基咪唑形成[Cu（acac）2（Im- 3）n = 2 ]反赤道加合物，而较大的2-甲基咪唑（Im- 2）和苯并咪唑（Im- 4）仅形成[Cu（acac）2（Im- 2,4）n = 1 ]单加合物。因此，我们的数据表明，底物结构的细微变化导致配位行为的可控变化，进而可以合理设计用于催化，成像和医学的复合物。
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