Rational Design of Fluorophores for In Vivo Applications - Progress in Molecular Biology and Translational Science - page 89

OR 1

N

N R N

N Si N

N R N

N

SO 3 Na

R = OSi

N

SO 3 Na

NaO 3 S

l abs = 689 nm

= 165,000 M − 1 cm − 1

e

l em = 700 nm
F f = 0.14

Solvent: PBS

Ref. 213

Chart 3.9 Structure and optical properties of representative phthalocyanine

fluorophore.

monofunctional, bioconjugatable derivatives. Finally, similar toporphyrins and
hydroporphyrins, phthalocyanines tend to be photocytotoxic. 167 Recent pro-
gress in the chemistry of phthalocyanines has partially solved the above-
mentioned issues. Nonaggregating, water-soluble phthalocyanines bearing
neutral, cationic, or anionic hydrophilic groups have been recently reported
by Vicente and coworkers 214,215 and Ng and coworkers. 216 The water
solubility and suppressed aggregation have been achieved by installing bulky
groups, containing poly(ethylene) glycols, 216 quarternary pyridinium
(cationic), 215 or carboxylate (anionic) 214 groups on the periphery of the
macrocycle. Another notable approach to suppress aggregation and impose
water solubility relies on the synthesis of silicon complexes of
phthalocyanines and attaching hydrophilic groups as axial ligands to the
central silicon atom (see Chart 3.9 for an example). 213,217-219 As axial ligands
are situated centrally above and below the phthalocyanine plane, they
prevent aggregation by steric repulsion. PEG, 217,219 sulfonic group-

terminated alkyl amines, 213 or polyamines 218 have been used as axial

hydrophilic groups.
Recently, notable progress has been made on the synthesis of mono-
functional phthalocyanine derivatives. Hammer and coworkers reported