Effect of Concentration on Isomerization of Rhodanine Derivatives of Merocyanine Dyes in Polar Solvents
Figure 5
Molar extinction coefficient of solutions of (a) 1 in DMF: (1)—10−5 M; (2)—2.0 × 10−5 M; (3)—2.9 × 10−5 M; (4)—4.8 × 10−5 M; (5)—1.0 × 10−4 M; (6)—1.0 × 10−3 M; (7)—1.0 × 10−5 M in binary solution of DMF/water (1 : 100 vol.%). An isosbestic point at 478 nm clearly evidences two forms of the dye molecules in the DMF solution at moderate concentrations; (b) 2 in DMF: (1)—9.1 × 10−7 M; (2)—1.0 × 10−5 M; (3)—2.1 × 10−5 M; (4)—3.15 × 10−5 M; (5)—1.0 × 10−4 M; (6)—1.0 × 10−3 M; (7)—1.0 × 10−5 M in binary solution of DMF/water (1 : 100 vol.%). An isosbestic point at 494 nm clearly evidences two forms of the dye molecules in the DMF solution at moderate concentrations; (c) 1 in NMP: (1)—10−5 M; (2)—2.0 × 10−5 M; (3)—3.8 × 10−5 M; (4)—5.7 × 10−5 M; (5)—7.4 × 10−5 M; (6)—9.0 × 10−5 M; (7)—1.0 × 10−3 M; (d) 2a in DMF: (1)—10−6 M; (2)—10−5 M; (3)—10−4 M.
