Stepwise assembly of unsymmetrical supramolecular arrays containing porphyrins and coordination compounds

The stepwise coordination of meso-4'-pyridyl/phenyl porphyrins (4'-PyPs) to different. metal centers proved to he an efficient synthetic approach leading to unsymmetrical arrays containing porphyrins and coordination compounds, The first step of this process, treatment of 4'-PyPs with a less than stoichiometric amount of cis, fac-RuCl2(Me-2-SO)(3)(CO) (1), leads to the selective coordination of [cis,cis,cis-RuCl2(Me2SO)(2)(CO)] fragments ([Ru]) to some of the peripheral 4'-N sites of the 4'-PyPs. Column separation afforded four partially ruthenated 4'-PyPs in pure form: 4'-cis-DPyP[Ru] (2), 4'-trans-DPyPr[Ru] (3), (4'-TPyP)[Ru] (4), and (4'-TPyP)[Ru](3) (5). These compounds, which have residual unbound peripheral 4'-N(py) sites (either one or three), were allowed to react with other metal centers that may belong either to a metalloporphyrin or to a coordination compound. When building blocks 2-5 were treated with [Ru(TPP)(CO)(EtOH)] (TPP = meso-tetraphenylporphyrin) in chloroform at room temperature, axial coordination of Ru(TPP)(CO) units ((Ru)) to the available 4'-N(py)(py) sites readily occurred, generating the following arrays containing both perpendicular porphrins and coordination compounds: (Ru)-(mu-4'-cis-DPyP)[Ru], (Ru)(mu-4'-trans-DPyP)[Ru], (Ru)(3)(mu-4'-DPyP)[Ru], and (Ru)(mu-4'-TPyP)[Ru](3). Furthermore, building blocks 2, 3, and 5 were treated with a series of coordination compounds capable of binding two pyridylporphyrins either cis to each other (trans-RuCl2(Me2SO)(4) and trans,cis,cis-RuCl2(Me2SO)(2)(CO)(2)) or trans to each other (trans-PdCl6(C6H5CN)(2)). Homo- (Ru) and heterobimetallic (Ru-Pd) arrays with as many as seven metal atoms (six Ru and one Pd) and two 4'-PyPs were obtained as follows: trans,cis,cis-RuCl2(Me2SO)(2)(4'cis-DPyP[Ru])(2), trans,cis,cis-RuCl2(Me2SO)(2)(4'-trans-DPyP[Ru])(2) trans,cis,cis-RuCl2(CO)(4'-cis-DPyP[Ru])(2) and trans-PdCl2(4'-TPyP[Ru](3))(2), All the products were thoroughly characterized by H-1 NMR spectroscopy. Since the [Ru] fragment is chiral, diastereomers are formed when two or more [Ru] units are bound to a porphyrin. We found that when two 4'-cis-DPyP[Ru] (2) units are coordinated cis to each other on the same metal center, the mutual anisotropic effect of the cis porphyrins differentiates the sulfoxide methyl resonances for the two forms; These and other results indicate that the pyridyl units react independently of the presence or absence of a substituent on the other py rings. Thus, the synthetic strategy should be a general method for linking diverse metal centers through pyridylporphyrins.