Silicon and Zinc Coordination to Peripheral Catechol Sites of (2,3,9,10,16,17,23,24-Octahydroxyphthalocyaninato)nickel(II). Phthalocyanine Coordination Chemistry at the Edge
作者:Michael Ruf、Andrew M. Lawrence、Bruce C. Noll、Cortlandt G. Pierpont
DOI:10.1021/ic980036g
日期:1998.4.20
(2.3.9.10.16,17,23,24-Octahydroxyphthalocyaninato)nickel (NiPc(OH)(8)) has been prepared by demethylation of (octamethoxyphthalocyaninato)nickel(II). Silylation of peripheral oxygen atoms using dimethyl-tert-butylsilyl chloride gave NiPc(OSi(t-Bu)Me-2)(8) as a convenient precursor to NiPc(OH)(8) with high solubility in hydrocarbon solvents. The coordination properties of peripheral catechol sites were investigated by treating NiPc(OH)s with Tp(Cum,Me)Zn(OH). A model study was first carried out by adding 5,6-dihydroxyphthalimide (H(2)PhtCat) to Tp(Cum,Me)Zn(OH). Partial deprotonation occurred to give Tp(Cum,Me)Zn(HPhtCat). Further deprotonation with NMe4(OH) gave (NMe4)[Tp(Cum,ME)Zn(PhtCat)] as the methanol solvate. H-1 NMR spectra recorded on Tp(Cum,Me)Zn(HPhtCat) show sharp resonances for equivalent arms of the Tp(Cum,Me) ligand, while Tp(Cum,Me) resonances for (NMe4)[Tp(Cum,Me)Zn(PhtCat)] appear broadened by slow site exchange about the strongly chelated catecholate ligand. Similarly, the reaction between NiPc(OH)(8) and Tp(Cum,Me)Zn(OH) occurred with partial deprotonation to give NiPc(OH)(4)(OZnTp(Cum,Me))(4) Structural characterization on crystals obtained from acetonitrile showed that Zn ions bond to single ring oxygen atoms at two sites and that they chelate to adjacent oxygen atoms at the other two ring sites. Cumenyl i-propyl substituents of the Tp(Cum,Me) ligands form hydrophobic pockets above and below the central metal of the phthalocyanine ring. These sites are occupied by acetonitrile solvent molecules positioned with hydrogen atoms directed toward the Ni atom in the crystal structure of the complex obtained by crystallization from a dichloromethane/acetonitrile solution. Addition of base to NiPc(OH)(4)(OZnTp(Cum,Me))(4) results in deprotonation of the remaining four OH groups and substantial red shifts for electronic transitions in the 400 and 600 nm regions of the phthalocyanine ring. Broadened H-1 NMR resonances for arms of the Tp(Cum,Me) ligands point to a chelated structure for the Zn atoms of (NMe4)(4)[NiPc(O(2)ZnTp(Cum,Me))(4)].
(2.3.9.10.16,17,23,24-八羟基酞菁)镍(NiPc(OH)₈)是通过(八甲氧基酞菁)镍(II)的脱甲基作用制备而成。使用双甲基-叔丁基硅基氯对周边的氧原子进行硅化处理,得到了NiPc(OSi(t-Bu)Me₂)₈作为一种方便制备NiPc(OH)₈的前驱体,且其在烃类溶剂中具有较高的溶解度。
通过将Tp(Cum,Me)Zn(OH)与NiPc(OH)s反应,研究了周边 catechol 位置的配位性质。首先进行了一项模型研究,将5,6-二羟酞酰亚胺(H₂PhtCat)添加到Tp(Cum,Me)Zn(OH)中。部分脱质子化发生,生成Tp(Cum,Me)Zn(HPhtCat)。进一步使用NMe₄(OH)脱质子化,得到了(NMe₄)[Tp(Cum,Me)Zn(PhtCat)]作为甲醇溶剂的配合物。记录的Tp(Cum,Me)Zn(HPhtCat)的¹H NMR谱图显示,Tp(Cum,Me)配体的等效臂展有尖锐的共振,而(NMe₄)[Tp(Cum,Me)Zn(PhtCat)]的Tp(Cum,Me)共振由于与强螯合catecholate配体的慢位点交换而变宽。
类似地,NiPc(OH)₈与Tp(Cum,Me)Zn(OH)反应伴随部分脱质子化,生成NiPc(OH)₄(OZnTp(Cum,Me))₄。对从乙腈中获得的晶体进行结构表征,结果显示锌离子在两个位点与单环氧原子键合,并在另外两个环位点与相邻氧原子螯合。Tp(Cum,Me)配体的异丙基Cumenyl取代基在酞菁环中心金属的上方和下方形成疏水包,这些位点被乙腈溶剂分子占据,在复杂晶体结构中,氢原子朝向镍原子,该结构由二氯甲烷/乙腈溶液中析出。
向NiPc(OH)₄(OZnTp(Cum,Me))₄中添加碱,导致剩余四个OH基团脱质子化,并在酞菁环的400 nm和600 nm区域的电子跃迁中出现显著的红移。对(NMe₄)₄[NiPc(O₂ZnTp(Cum,Me))₄]中的Zn原子的结构表征,Tp(Cum,Me)配体的¹H NMR共振变宽,表明其形成了螯合结构。