## 2 Materials and Methods
### Chemistry
IR \(v_{\max}\) (KBr): 2955, 2930, 1553, 1506, 1443, 1379, 1352, 1258, 1184, 1153, 1119, 1030 cm\({}^{-1}\); \({}^{1}\)H-NMR (600 MHz, CDCl\({}_{3}\)) \(\delta\): 8.65 (1H, br s, ArH), 7.92 (1H, s, ArH), 7.88 (1H, d, \(J\) = 9.0 Hz, ArH), 7.63 (2H, t, \(J\) = 7.5 Hz, ArH), 7.48 (1H, t, \(J\) = 7.2 Hz, ArH), 7.41 (1H, d, \(J\) = 9.0 Hz, ArH), 7.35-7.33 (2H, m, ArH), 6.08 (1H, s, C=CH), 5.55 (1H, s, C=CH), 4.61 (3H, s, OCH\({}_{3}\)), 4.39 (2H, t, \(J\) = 7.2 Hz, NCH\({}_{2}\)(CH\({}_{2}\))\({}_{4}\)CH\({}_{3}\)), 4.32 (2H, br s, NCH\({}_{2}\)(CH\({}_{2}\))\({}_{4}\)CH\({}_{3}\)), 1.81 (4H, qt, NCH\({}_{2}\)CH\({}_{2}\)(CH\({}_{2}\))\({}_{3}\)CH\({}_{3}\)), 1.56 (2H, qt, N(CH\({}_{2}\))\({}_{2}\)CH\({}_{2}\)(CH\({}_{2}\))\({}_{2}\)CH\({}_{3}\)), 1.46-1.36 (6H, m, N(CH\({}_{2}\))\({}_{2}\)(CH\({}_{2}\))\({}_{2}\)CH\({}_{3}\)), 1.31 (4H, br s, N(CH\({}_{2}\))\({}_{4}\)CH\({}_{2}\)CH\({}_{3}\)), 0.92 (3H, t, \(J\) = 6.0 Hz, N(CH\({}_{2}\))\({}_{5}\)CH\({}_{3}\)), 0.86 (3H, t, \(J\) = 6.3 Hz, N(CH\({}_{2}\))\({}_{5}\)CH\({}_{3}\)) ppm; \({}^{13}\)C-NMR (150.91 MHz, CDCl\({}_{3}\)) 8: 177.91, 162.08, 158,77, 157.49, 151.28, 141.05 (ArCH), 140.59, 138.40, 137.32 (ArCH), 134.84 (ArCH), 128.13 (ArCH), 128.00, 126.81, 125.54 (ArCH), 125.11 (ArCH), 122.27 (ArCH), 119.81, 117.75 (ArCH), 113.27 (ArCH), 91.83 (C=CH), 89.69, 86.50 (C=CH), 61.30 (OCH\({}_{3}\)), 48.95 (NCH\({}_{2}\)), 47.12 (NCH\({}_{2}\)), 31.43 (CH\({}_{2}\)), 31.34 (CH\({}_{2}\)), 31.34 (CH\({}_{2}\)), 31.34 (CH\({}_{2}\)), 31.36 (CH\({}_{2}\)), 27.84 (CH\({}_{2}\)), 27.12 (CH\({}_{2}\)), 26.30 (CH\({}_{2}\)), 26.16 (CH\({}_{2}\)), 22.46 (CH\({}_{2}\)), 22.39 (CH\({}_{2}\)), 13.94 (CH\({}_{3}\)), 13.91 (CH\({}_{3}\)) ppm; HRESI-TOFMS \(m\): 679.18313 (M-CF\({}_{3}\)SO\({}_{3}\))\({}^{+}\) (C\({}_{35}\)H\({}_{40}\)IN\({}_{2}\)O\({}_{2}\)S\({}^{+}\), calc. 679.18497). 1.3. Synthesis of 2-[(2-amino-3-[(1-hexyl-6-iodoquinolin-2(1\(H\))-ylidene)methyl]-4-oxocyclobut-2-en-1-ylidene)methyl]-3-hexylbenzothiazol-3-ium trifluoromethanesulfonate (**12**)  
To a solution of \(O\)-methylated squareaine cyanine dye **11** (0.20 g, 0.24 mmol) in anhydrous CH\({}_{2}\)Cl\({}_{2}\), under N\({}_{2}\) atmosphere at r.t., was added an excess of 2 M ammonia solution in MeOH (0.54 mL, 1.08 mmol). The reaction mixture was stirred at r.t. for 22 h and then washed with cold water. The organic layer was dried over anhydrous Na\({}_{2}\)SO\({}_{4}\), and the solvent was removed under reduced pressure. The product was recrystallized from CH\({}_{2}\)Cl\({}_{2}\)/MeOH. Yield: 65%. Green crystals. M.p. 282-285 \({}^{\circ}\)C (dec.). Vis \(\lambda_{\max}\) (DMSO): 705 nm, log \(\varepsilon\) = 5.17. Vis \(\lambda_{\max}\) (DMEM): 619 nm. Vis \(\lambda_{\max}\) (ACN): 686 nm, log \(\varepsilon\) = 5.36. Vis \(\lambda_{\max}\) (ACT): 690 nm, log \(\varepsilon\) = 5.36. Vis \(\lambda_{\max}\) (DCM): 694 nm, log \(\varepsilon\) = 5.38. Vis \(\lambda_{\max}\) (DMF): 700 nm, log \(\varepsilon\) = 5.31. Vis \(\lambda_{\max}\) (DXN): 706 nm, log \(\varepsilon\) = 5.27. Vis \(\lambda_{\max}\) (EtOH): 693 nm, log \(\varepsilon\) = 5.38. Vis \(\lambda_{\max}\) (MeOH): 687 nm, log \(\varepsilon\) = 5.36. Vis \(\lambda_{\max}\) (THF): 702 nm, log \(\varepsilon\) = 5.26.