Kemp’s triacidic imides

The hydrolysis of p-nitrophenyl acetate and bis(p-nitrophenyl phosphate) are frequently used to probe hydrolytic activity. A problem with some other dinuclear systems is that the Zn units are held together by bridging ligands which can be cleaved on reaction with the substrate.440 This is not the case in a ditopic ligand such as those designed by Lippard and co-workers based on Kemp s triacid imide with a xylyl spacer.441,442 Both zinc dimers and mixed metal dimers were formed and a structure characterized with a bridging phosphodiester (Figure 6). 

Scheme 2.8 Examples of ligands used to model the carboxylate coreofcarboxylate-bridged dinuclearironenzymes (a) R3XDK[for R = CH3 H2XDK = m-xylenediamine bis(Kemp s triacid) imide] [57] (b) differently substituted terphenyl-based ligands (e.g. for R1 = CH3, R2 = H TolArCOOH) [48].

Several dinuclear Mn11 complexes based on the dinucleating L9 ligand [L9 = m-xylenediamine bis(Kemp s triacid imide)] have a (p.-carboxylato)2 core [lOOp] (Figure 18). 

The final iron cage discussed is the largest known ferric wheel. The octadecanuclear wheel, [Fe(0H)(XDK)Fe2(0Me)4(02CMe)2]e (70) [XDK = the dianion of m-xylylenediamine bis(Kemp s triacid imide) see Scheme 2] (164), shown in Fig. 29, is made from reaction of the di-nuclear iron complex of XDK with [NEt4](02CMe) in methanol, followed... 

Complexes incorporating a constrained bis-carboxylate ligand, ZrX2(XDK) (X = Bn, NMe2 XDK = m-xylylenediamine bis(Kemp s triacid imide)) and Zr(XDK)2 have been synthesized and characterized structurally. This ligand was derived from Kemp s tri-acid imide derivative of m-xylylenediamine (92) and shown to chelate through the two carboxylic acid fragments.483... 

Fe7(PDK)2Cl8(H20)2] (PDK is a porphyrin substituted with Kemp s triacid imide) contains a pentanuclear Fe square-based pyramid, held together by chlorides and carboxylates which are derived from the PDK ligands. The final two Fe centers sit at the centers of the porphyrin rings. The cage is mixed valent, with two Fe and five Fe centers. 

Figure 13 The recognition between the Kemp s triacid imide in the activated ester 4 and the adenine base in 5 drives the formation of template 6 either through the binary complex [4-5] or through the corresponding [4-5-6] complex (shown as pathway III in Figure 14).

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