Shiren Kazushi, Tanaka Koji
Institute for Molecular Science and CREST, Japan Science and Technology Corporation (JST), 38 Nishigonaka, Myodaiji, Okazaki, Aichi 444-8585, Japan.
Inorg Chem. 2002 Nov 4;41(22):5912-9. doi: 10.1021/ic020308m.
A series of aqua-Cr(III)-dioxolene complexes, Cr(OH(2))(3,5-Bu(2)SQ)(trpy)(2) (1s), [Cr(OH(2))(3,5-Bu(2)Cat)(trpy)]ClO(4) (1c), Cr(OH(2))(3,6-Bu(2)SQ)(trpy)(2) (2), [Cr(OH(2))(Cat)(trpy)]ClO(4) (3), [Cr(OH(2))(Cl(4)Cat)(trpy)]ClO(4) (4), Cr(OH(2))(3,5-Bu(2)SQ)(Me(3)-tacn)(2) (5), [Cr(OH(2))(Cat)(Me(3)-tacn)]ClO(4) (6), and [Cr(OH(2))(Cl(4)Cat)(Me(3)-tacn)]ClO(4) (7) (Bu(2)SQ = di-tert-butyl-o-benzosemiquinonate anion, Bu(2)Cat = di-tert-butylcatecholate dianion, Cat = catecholate dianion, Cl(4)Cat = tetrachlorocatecholate dianion, trpy = 2,2':6',2' '-terpyridine, and Me(3)-tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane), were prepared. On the basis of the crystal structures, redox behavior, and elemental analyses of these complexes, dioxolene in 1c, 3, 4, 6, and 7 coordinated to Cr(III) as the catechol form, and the ligand in 1s, 2, and 5 was linked to Cr(III) with the semiquinone form. All the aqua-Cr(III) complexes reversibly changed to the hydroxo-Cr(III) ones upon dissociation of the aqua proton, and the pK(a) value of the aqua-Cr(III) complexes increased in the order 6 > 3 approximately 1c > 7 > 5 approximately 4 > 1s. Hydroxo-Cr(III)-catechol complexes derived from 1c, 3, 4, 6, and 7 did not show any signs of dissociation of their hydroxy proton. On the other hand, hydroxo-Cr(III)-semiquinone complexes were reduced to hydroxo-Cr(III)-catechol in H(2)O/THF at pH 11 under illumination of visible light.
制备了一系列水合铬（III）-二氧戊环配合物，即Cr(OH₂)(3,5-Bu₂SQ)(trpy)₂ (1s)、[Cr(OH₂)(3,5-Bu₂Cat)(trpy)]ClO₄ (1c)、Cr(OH₂)(3,6-Bu₂SQ)(trpy)₂ (2)、[Cr(OH₂)(Cat)(trpy)]ClO₄ (3)、[Cr(OH₂)(Cl₄Cat)(trpy)]ClO₄ (4)、Cr(OH₂)(3,5-Bu₂SQ)(Me₃-tacn)₂ (5)、[Cr(OH₂)(Cat)(Me₃-tacn)]ClO₄ (6) 和 [Cr(OH₂)(Cl₄Cat)(Me₃-tacn)]ClO₄ (7)（其中Bu₂SQ = 二叔丁基邻苯半醌阴离子，Bu₂Cat = 二叔丁基儿茶酚二阴离子，Cat = 儿茶酚二阴离子，Cl₄Cat = 四氯儿茶酚二阴离子，trpy = 2,2':6',2''-三联吡啶，Me₃-tacn = 1,4,7-三甲基-1,4,7-三氮杂环壬烷）。基于这些配合物的晶体结构、氧化还原行为和元素分析，1c、3、4、6和7中的二氧戊环以儿茶酚形式与Cr(III)配位，而1s、2和5中的配体以半醌形式与Cr(III)相连。所有水合铬（III）配合物在水合质子解离后可逆地转变为羟基铬（III）配合物，水合铬（III）配合物的pKa值按6 > 3 ≈ 1c > 7 > 5 ≈ 4 > 1s 的顺序增加。由1c、3、4、6和7衍生的羟基铬（III）-儿茶酚配合物未显示出其羟基质子解离的任何迹象。另一方面，在可见光照射下，羟基铬（III）-半醌配合物在pH 11的H₂O/THF中被还原为羟基铬（III）-儿茶酚配合物。
