“…On the other side, trimethine (bis trimethine) cyanine dyes recorded absorption bands in regions (370-620 nm) and (370-630 nm) (Table 1). This indicates that the value of absorption bands, position and molar extinction coefficient was influenced by several factors, such as: the nature of heterocyclic quaternary residue (A), electron withdrawing or donating groups present in the molecule, the number of methine units and the number of charge transfer pathwayy (Powar et al, 2009;Gomaa, 2014;Henary et al, 2013;Gomaa et al, 2012;Ahmed et al, 2018;Shindy et al, 2019;Shindy et al, 2017;Soriano et al, 2016;Gomaa, 2019). So, the absorption spectra of dyes (4b, d), (5b, d), (8b, d) and (9b, d) is a red-shifted to dyes (4a, c), (5a, c), (8a, c) and (9a, c) respectively.…”