Mondal Biplab, Puranik Vedavati G, Lahiri Goutam Kumar
Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai-400076, India.
Inorg Chem. 2002 Nov 4;41(22):5831-6. doi: 10.1021/ic020351+.
The reaction of Ru(trpy)Cl(3) (trpy = 2,2':6',2"-terpyridine) with the pyridine-based imine function N(p)C(5)H(4)-CH=N(i)-NH-C(6)H(5) (L), incorporating an NH spacer between the imine nitrogen (N(i)) and the pendant phenyl ring, in ethanol medium followed by chromatographic work up on a neutral alumina column using CH(3)CN/CH(2)Cl(2) (1:4) as eluent, results in complexes of the types Ru(trpy)(L')(2) (1) and [Ru(trpy)(L)Cl]ClO(4) (2). Although the identity of the free ligand (L) has been retained in complex 2, the preformed imine-based potentially bidentate ligand (L) has been selectively transformed into a new class of unusual imine-amidine-based tridentate ligand, N(p)C(5)H(4)-CH=N(i)-N(C(6)H(5))C(CH(3))=N(a)H (L'), in 1. The single-crystal X-ray structures of the free ligand (L) and both complexes 1 and 2 have been determined. In 2, the sixth coordination site, that is, the Cl(-) function, is cis to the pyridine nitrogen (N(p)) of L which in turn places the NH spacer away from the Ru-Cl bond, whereas, in 1, the corresponding sixth position, that is, the Ru-N(a) (amidine) bond, is trans to the pyridine nitrogen (N(p)) of L'. The trans configuration of N(a) with respect to the N(p) of L' in 1 provides the basis for the selective L --> L' transformation in 1. The complexes exhibit strong Ru(II) --> pi* (trpy) MLCT transitions in the visible region and intraligand transitions in the UV region. The lowest energy MLCT band at 510 nm for 2 has been substantially blue-shifted to 478 nm in the case of 1. The reversible Ru(III)-Ru(II) couples for 1 and 2 have been observed at 0.80 and 0.59 V versus SCE, respectively. The complexes are weakly luminescent at 77 K, exhibiting emissions at lambda(max), 598 nm [quantum yield (Phi) = 0.43 x 10(-2)] and 574 nm (Phi = 0.28 x 10(-2)) for 1 and 2, respectively.
Ru(trpy)Cl(3)（trpy = 2,2':6',2"-三联吡啶）与基于吡啶的亚胺官能团N(p)C(5)H(4)-CH=N(i)-NH-C(6)H(5)（L）在乙醇介质中反应，该官能团在亚胺氮（N(i)）和侧苯基环之间含有一个NH间隔基，然后使用CH(3)CN/CH(2)Cl(2)（1:4）作为洗脱剂在中性氧化铝柱上进行色谱分离，得到Ru(trpy)(L')(2)（1）和[Ru(trpy)(L)Cl]ClO(4)（2）类型的配合物。尽管游离配体（L）的结构在配合物2中得以保留，但预先形成的基于亚胺的潜在双齿配体（L）在配合物1中已被选择性地转化为一类新型的不寻常的基于亚胺-脒的三齿配体，N(p)C(5)H(4)-CH=N(i)-N(C(6)H(5))C(CH(3))=N(a)H（L'）。已测定了游离配体（L）以及配合物1和2的单晶X射线结构。在配合物2中，第六个配位点，即Cl(-)官能团，与L的吡啶氮（N(p)）呈顺式，这使得NH间隔基远离Ru-Cl键，而在配合物1中，相应的第六个位置，即Ru-N(a)（脒）键，与L'的吡啶氮（N(p)）呈反式。配合物1中N(a)相对于L'的N(p)的反式构型为1中L→L'的选择性转化提供了基础。这些配合物在可见光区域表现出强烈的Ru(II)→π*（trpy）MLCT跃迁，在紫外区域表现出配体内跃迁。配合物2在510 nm处的最低能量MLCT带在配合物1的情况下已大幅蓝移至478 nm。已观察到配合物1和2的可逆Ru(III)-Ru(II)电对相对于SCE分别在0.80和0.59 V处。这些配合物在77 K时发光较弱，配合物1和2分别在λ(max) = 598 nm[量子产率（Φ） = 0.43×10(-2)]和574 nm（Φ = 0.28×10(-2)）处发射。
