Templated formation of multi-porphyrin assemblies resembling a molecular universal joint

The rigid bis-porphyrinic host 2 forms 1:1 complexes with rigid 5,15-bis(4- pyridyl)porphyrins and both 1:1 and 2:1 complexes with tetrapyridylporphyri n 4, with the latter complex providing a new example of a self-assembled sy stem containing an enclosed molecular environment.