“…2-((E)-2-((E)-2-chloro-3-(2-((E)-1,3,3-trimethylindolin-2-ylidene)ethylidene)cyclohex-1-en-1-yl)vinyl)-1,3,3-trimethyl-3H-indol-1-ium iodide, 4a : was synthesized as previously described. Stability in solution of indolium heptamethine cyanines and related pH-sensitive systems 26 1 H NMR (400 MHz, DMSO- d 6 ) δ 1.67 (s, 12 H), 1.85 (m, 2 H), 2.72 (t, J = 6.0 Hz, 4 H), 3.68 (s, 6 H), 6.30 (t, J = 14.4 Hz, 2 H), 7.28 (m, 2 H), 7.44 (m, 4 H), 7.62 (d, J = 7.2 Hz, 2 H), 8.25 (d, J = 14.4 Hz, 2 H).…”