Spectroscopic studies of the multiporphyrin arrays at the air–water interface and in Langmuir–Blodgett films

Abstract

We describe the spectroscopic studies of the monolayers and Langmuir–Blodgett (LB) films of tetrapyridylporphyrin (TPyP), its mixture with a phospholipid (DPPTE) and the (2DPPTE–)Cd 2+–TPyP multiporphyrin arrays. Red-shift of the porphyrin Soret band was 23–27 nm in the monolayers and LB films of TPyP or the TPyP–2DPPTE mixture; while it was only 3–11 nm in the monolayers and LB films of the (2DPPTE–)Cd 2+–TPyP multiporphyrin arrays. This difference has been attributed to the weakened TPyP–TPyP interaction in the multiporphyrin arrays. Immersion of an intercalation phospholipid layer in the matrix of the monolayers and LB films of TPyP or the Cd 2+–TPyP multiporphyrin array further reduced this interaction and made it possible for the fabrication of three-dimensional layered multiporphyrin arrays. The fluorescence spectra of TPyP in the LB films of the (2DPPTE–)Cd 2+–TPyP multiporphyrin array were also quite different from those in the solutions and TPyP(–2DPPTE) LB films. The average molecular orientation angle θ between the mean porphyrin plane and the substrate surface was approximately 26–31° for the LB films of the TPyP and the Cd 2+–TPyP multiporphyrin array, and approximately 35–38° for the LB films of the TPyP–2DPPTE and 2DPPTE–Cd 2+–TPyP multiporphyrin array.