ABSTRACT

Chromophoric π -conjugated macrocycles have potential applica-

tions such as optical, magnetic, conductive materials, and sen-

sors for chemical and physical stimuli, originating from the unique

π -electronic networks on the cyclic structure [1-12]. In a vari-

ety of macrocycles, porphyrins with 22 π -electrons, which obey

Hu¨ckel’s rule on aromaticity, have attracted great interest, since

they play significant roles in nature such as in green leaves and

red blood cells [13-16]. Light-harvesting antenna complexes with

well-ordered metalloporphyrin derivatives allow efficient energy

migration over many pigments within the antenna system toward

a reaction center, while hemoglobin-carrying heme groups, con-

sisting of an iron porphyrin derivative, allow oxygen transport

in the body. These biological functions originate from the unique

π -electronic structure and guest-hosting properties of the metal-

loporphyrin, together with well-ordered arrangements of the multi

porphyrins. The characteristic π -electronic features of porphyrins

are variable upon attachment of certain substituents at the periph-

ery of the porphyrin ring, modification of the macrocyclic ring,

and insertion or exchange of the metal ion of the porphyrin center

[17-20]. With these interesting features of the porphyrins in mind,

a variety of porphyrin-based chemical sensors, which can spectro-

scopically discriminate gases, metal ions, anions, pH, and molecules

have been developed. These sensing systems using porphyrin and

its analogues are achieved by the dynamic interaction with guest

species in the molecular level. In this research background, the

author has interested in sensoring not only chemical species but also

physical stimuli by using supramolecular multiporphyrin architec-

tures. The supramolecular architectures, containing the porphyrin

pigments, are suitable for use as chemical sensors for direct visual-

ization and/or indirect spectroscopic visualization of dynamicmole-

cular motion, assembly, interaction, and orientation. This chapter

presents interesting unique features of the supramolecular mul-

tiporphyrin assemblies, which can chemically sense solvent clus-

ters in molecular recognition, and physically sense temperature and

microscopic solvent fluidics induced by stirring, shaking, and sound

irradiation.