Structural and Kinetic Studies of Spin Crossover in an Iron(II) Complex with a Novel Tripodal Ligand.
Structural and Kinetic Studies of Spin Crossover in an Iron(II) Complex with a Novel Tripodal Ligand.
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具有新型三足配体的铁（II）配合物中自旋交叉的结构和动力学研究。
DOI：
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发表时间：
1996
影响因子：
4.6
通讯作者：
Jonathan G. Carroll
中科院分区：
文献类型：
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作者：
Ala Al;K. B. Jensen;J. McGarvey;H. Toftlund;Bent Jensen;S. Bell;Jonathan G. Carroll
研究了新型三足配体1,1,1-三(（N-（2-吡啶基甲基）-N-甲基氨基）甲基乙烷（tptMetame） Fe（II）配合物中构型和配体构象对(1)A(1)右鱼叉与(5)T(2)自旋交叉动力学的影响。尽管有六个螯合环和三个手性氮原子，但只观察到络合离子的一个对映体对异构体，δ， SSS和λ， RRR。形成复杂结构上部“帽”的三个环的构象可以相对于3倍分子轴指定为delta或lambda。300 K和153 K下的x射线数据，高于和低于自旋跃迁的临界温度，表明配体“cap”的构象与配合物的绝对构型相同，LS (（1)A(1)）和HS (（5)T(2)）异构体都具有相同的Lambdalambda(cap)（或delta(cap)）组合。分子力学计算进一步表明，在LS和HS同分异构体的所有Fe-N距离上，λ λ (CAP)（或δ δ (CAP)）组合的配体能量最低。在293 ~ 170 K温度范围内的溶液中进行了自旋交叉弛豫时间的测量。观察到的单相弛豫痕迹也与自旋交叉过程中复合物的绝对构型保持不变相一致。
Configurational and ligand conformational influences on the kinetics of (1)A(1) right harpoon over left harpoon (5)T(2) spin crossover in the Fe(II) complex with the novel tripodal ligand, 1,1,1-tris((N-(2-pyridylmethyl)-N-methylamino)methyl)ethane (tptMetame), have been explored. Despite having six chelate rings and three chiral nitrogen atoms, only one enantiomeric pair of isomers, Delta, SSS, and Lambda, RRR, of the complex ion is observed. The conformation of the three rings forming the upper "cap" of the complex structure can be assigned delta or lambda with respect to the 3-fold molecular axis. X-ray data at 300 and 153 K, above and below the critical temperature for the spin transition, show that the conformation of the ligand "cap" is the same as the absolute configuration of the complex, with the same Lambdalambda(CAP)(or Deltadelta(CAP)) combination prevailing for both the LS ((1)A(1)) and HS ((5)T(2)) isomers. Molecular mechanics calculations further show that the ligand energy remains lowest for this Lambdalambda(CAP) (or Deltadelta(CAP)) combination at all Fe-N distances over the range spanning the LS and HS isomers. Measurements of the spin crossover relaxation time have been carried out in solution over the temperature range 293-170 K. The observed monophasic relaxation traces are also consistent with the absolute configuration of the complex remaining unaltered during the spin crossover.