Axial ligand coordination, self-assembly

Self-Assembly of Porphyrins by Axial Ligand Coordination. 156... 

Supramolecular self-assembly was also observed in triphenyllead dimethyldithiophos-phinate, [Ph3PbS2PMe2]n(178)466. The dithiophosphinate ligand unsymmetrically bridges two lead atoms of adjacent molecules to give a polymeric chain with pentacoordinated lead centres. The coordination environment at lead is best described as that of a distorted trigonal bipyramid with the phenyl groups in the equatorial and the sulphur atoms in the axial positions. The Pb—S distances amount to 2.708(4) A and 3.028(4) A. 

The self-assembled diad formed by axial coordination of zinc naphthalocyanine (ZnNc) and fulleropyrrolidine bearing a coordinating imidazole ligand (Qolm) is a good example of a supramolecular system undergoing photoinduced electron... 

In addition to the mononuclear nodes conunonly known from coordination chemistry, multinuclear nodes are often encountered in coordination polymers (Figure 4). In general, these are self-assembled under the reaction conditions rather than introduced intact although this is not necessarily the case with polyoxometallate nodes. The dimetallic node is of some interest as it can enter into ihe network through coordination of additional donors at the two axial sites, or through the substituents on the carboxylate ligands. In other words, this unit can act as either a two node or a four node. 

Macrocyclic ligands, mac, are usually coordinated into the equatorial plane of the metal ions, the axial positions being occupied by weakly bonded ligands, which can be replaced by the cyano bridges. The self-assembly process involving ro 5-[M (wac)(H20)2] and [M(CN)6] ions yields 2D [M 3M2] networks. Within a layer, each mac)f moiety is linked to two [M (CN)6] ions in trans positions, and each [M(CN)6] ion is surrounded by three [M(wac)f units. If the three M. mac) units adopt a facial configuration around the M ion, then layers with a stair-shaped honeycomb architecture are formed mac stands for cyclam, 1,4,8,11-tetraazacyclotetradecane) (Fig. 36). A meridial arrangement of the three M mac)f moieties leads to flat brick-wall-like layers mac = 3,10-diethyl-l,3,5,8,10,12-hexaazacyclotetradecane (Fig. 37). ... 

---