A functionalized noncovalent macrocyclic multiporphyrin assembly from a dizinc(II) bis-porphyrin receptor and a free-base dipyridylporphyrin.
The bis-porphyrin system ZnP(2), in which two zinc porphyrins are connected by a phenanthroline linker in an oblique fashion, acts as a bifunctional receptor towards the complexation of free-base meso-5,10-bis(4'-pyridyl)-15,20-diphenylporphyrin (4'-cis DPyP). In solution, NMR spectroscopy evidenced quantitative formation of the tris-porphyrin macrocyclic assembly ZnP(2)(4'-cis DPyP), in which the two fragments are held together by two axial 4'-N(pyridyl)-Zn interactions. The remarkable stability of the edifice (an association constant of about 6x10(8) M(-1) was determined by UV/Vis absorption and emission titration experiments in toluene) is due to the almost perfect geometrical match between the two interacting units. The macrocycle was crystallized and studied by X-ray diffraction, which confirmed the excellent complementarity of the two components. Photoinduced energy transfer from the singlet excited state of the zinc porphyrin chromophores to the free-base porphyrin occurs with an efficiency of 98 % (k(en)=2x10(10) s(-1) in toluene, ambient temperature) with a mechanism consistent with a dipole-dipole process with a low orientation factor.
Iengo
Elisabetta
E
Dipartimento di Scienze Chimiche, Università di Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy.
Zangrando
Ennio
E
Alessio
Enzo
E
Chambron
Jean-Claude
JC
Heitz
Valérie
V
Flamigni
Lucia
L
Sauvage
Jean-Pierre
JP
D018360:Crystallography, X-Ray; D046911:Macromolecular Substances / Q000138:chemical synthesis / Q000737:chemistry; D013058:Mass Spectrometry; D008665:Metalloporphyrins / Q000138:chemical synthesis* / Q000737:chemistry; D008956:Models, Chemical; D013056:Spectrophotometry, Ultraviolet; D015032:Zinc / Q000737:chemistry*
D046911:Macromolecular Substances; D008665:Metalloporphyrins; D015032:Zinc