Inspection of the duality of a verdazyl-based radical in transition metal complexes:: A π* donor ligand and a magnetic partner
Inspection of the duality of a verdazyl-based radical in transition metal complexes:: A π* donor ligand and a magnetic partner
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DOI：
10.1021/ja802027u
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发表时间：
2008-08-06
影响因子：
15
通讯作者：
Robert, Vincent
中科院分区：
文献类型：
--
作者：
Rota, Jean-Baptiste;Norel, Lucie;Robert, Vincent
用从头算波函数方法分析了[M（hfac）（2）imvd（o）]（M = Mn，Ni; hfac =（1，1，1，5，5，5）六氟乙酰丙酮; imvd（o）= 3-（2 '-咪唑基）-1，5-二甲基-6-氧代维氮基）配合物中维氮基自由基与开壳过渡金属离子的结合行为.计算的交换偶合常数J（H = -JS（M）.Simvd（o）; J（Mn）（calcd）= -63 cm（-1），J（Ni）（calcd）= 205 cm（-1））与实验值（J（Mn）（exP）= -63 cm（-1），J（Ni）（exp）= 193 cm（-1））符合得很好.即使两个环都通过imvd（o）自由基的结合模式参与，自旋密度仍然基本上局限于富氮环。这种奇异性源于它的双齿配位特征。相关波函数的分析表明，verdazyl为基础的自由基作为一个pi* 供体配体，允许配体到金属的电荷转移，并排除金属配体的电荷转移。这反映了M-imvd（o）pi配位键的弱共价特征。从磁性的角度来看，贯穿空间交换控制了镍衍生物中高达153 cm（-1）的铁磁特性，正如从限于磁轨道的描述中所预期的那样。然而，Cl展开显示了Verdazyl部分上激发的双重态和四重态（自旋极化）的参与，这导致了显著的额外铁磁贡献（52 cm（-1））。在[Mn（hfac）（2）imvd（o）]类似物中，动力学交换产生的反铁磁贡献仅为观察到的交换耦合常数的三分之一。有必要引入动力学关联效应来定量地恢复该化合物中的交换相互作用。由于咪唑部分的π * 供体和自旋极化的字符占主导地位的咪唑部分的可忽略的极化率，它的结论是，非无辜性质的imvd（o）自由基是由verdazyl环部分举行。
The behavior of a verclazyl-based radical bound to open-shell transition metal ions in the structurally and magnetically characterized [M(hfac)(2)imvd(o)] (M = Mn, Ni; hfac = (1,1,1,5,5,5)hexafluoro-acetylacetonate; imvd(o) = 3-(2'-imidazolyl)-1,5-dimethyl-6-oxoverdazyl) complexes is rationalized using ab initio wave-function-based calculations analysis. The calculated exchange coupling constants J (H = -JS(M).Simvd(o); J(Mn)(calcd) = -63 cm(-1), J(Ni)(calcd), = 205 cm-1) are in excellent agreement with the experimental ones (J(Mn)(exP) = -63 cm(-1), J(Ni)(exp) = 193 cm(-1)). Even though both rings are involved through the binding mode of the imvd(o) radical, the spin density remains essentially localized on the nitrogen-rich ring. The singularity stems from its bidentate coordinating character. The analysis of the correlated wave function suggests that the verdazyl-based radical acts as a pi* donor ligand which allows ligand-to-metal charge transfer and excludes metal-to-ligand charge transfer. This reflects the weak covalent character of the M-imvd(o) pi coordination bond. From a magnetic point of view, the through-space exchange governs the ferromagnetic character in the Ni derivative up to 153 cm(-1) as expected from a description limited to the magnetic orbitals. Nevertheless, the Cl expansion displays the participation of excited doublet and quartet states (spin polarization) on the verdazyl moiety which leads to a significant additional ferromagnetic contribution (52 cm(-1)). In the [Mn(hfac)(2)imvd(o)] analogue, the antiferromagnetic contribution arising from kinetic exchange is only one-third of the observed exchange coupling constant. It is necessary to introduce dynamical correlation effects to quantitatively recover the exchange interaction in this compound. Since the pi* donor and spin-polarized characters of the verdazyl moiety dominate over the negligible polarizability of the imidazole part, it is concluded that the noninnocent nature of the imvd(o) radical is held by the verdazyl ring part.