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 lead ing to unsymmetrical arrays containing porphyrins and coordination compound s, The first step of this process, treatment of 4'-PyPs with a less than st oichiometric amount of cis, fac-RuCl2(Me-2-SO)(3)(CO) (1), leads to the sel ective coordination of [cis,cis,cis-RuCl2(Me2SO)(2)(CO)] fragments ([Ru]) t o some of the peripheral 4'-N sites of the 4'-PyPs. Column separation affor ded 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 co mpounds, which have residual unbound peripheral 4'-N(py) sites (either one or three), were allowed to react with other metal centers that may belong e ither to a metalloporphyrin or to a coordination compound. When building bl ocks 2-5 were treated with [Ru(TPP)(CO)(EtOH)] (TPP = meso-tetraphenylporph yrin) in chloroform at room temperature, axial coordination of Ru(TPP)(CO) units ((Ru)) to the available 4'-N(py)(py) sites readily occurred, generati ng the following arrays containing both perpendicular porphrins and coordin ation 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 bl ocks 2, 3, and 5 were treated with a series of coordination compounds capab le of binding two pyridylporphyrins either cis to each other (trans-RuCl2(M e2SO)(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 wit h as many as seven metal atoms (six Ru and one Pd) and two 4'-PyPs were obt ained as follows: trans,cis,cis-RuCl2(Me2SO)(2)(4'cis-DPyP[Ru])(2), trans,c is,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 tho roughly characterized by H-1 NMR spectroscopy. Since the [Ru] fragment is c hiral, 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 th e 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 r ings. Thus, the synthetic strategy should be a general method for linking d iverse metal centers through pyridylporphyrins.