The electronic interactions and excitation energy transfer (EET) processes of a variety of multi-porphyrin arrays with linear, cyclic and box architectures have been explored. Directly
meso
–
meso
linked linear arrays (
Z
N
) exhibit strong excitonic coupling with an exciton coherence length of approximately 6 porphyrin units, while fused linear arrays (
T
N
) exhibit extensive
π
-conjugation over the whole array. The excitonic coherence length in directly linked cyclic porphyrin rings (
CZ
N
) was determined to be approximately 2.7 porphyrin units by simultaneous analysis of fluorescence intensities and lifetimes at the single-molecule level. By performing transient absorption (TA) and TA anisotropy decay measurements, the EET rates in
m
-phenylene linked cyclic porphyrin wheels
C12ZA
and
C24ZB
were determined to be 4 and 36 ps
−1
, respectively. With increasing the size of
C
N
ZA
, the EET efficiencies decrease owing to the structural distortions that produce considerable non-radiative decay pathways. Finally, the EET rates of self-assembled porphyrin boxes consisting of directly linked diporphyrins,
B1A
,
B2A
and
B3A
, are 48, 98 and 361 ps
−1
, respectively. The EET rates of porphyrin boxes consisting of alkynylene-bridged diporphyrins,
B2B
and
B4B
, depend on the conformation of building blocks (planar or orthogonal) rather than the length of alkynylene linkers.
Single–motor mechanics and models of the myosin motor
