TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (Claimed): Preparation of (I) comprises: reacting a first compound that is substituted 4,5,9,10-tetrabromo-benzo(lmn)(3,8) phenanthroline-1,3,6,8-tetraone of formula (IIe) with a second compound that is amino compounds of formula (R3-C(=X2)-NH2) (III) to form (I); or reacting a substituted 4,9-dibromo-benzo(lmn)(3,8)phenanthroline-1,3,6,8-tetraone of formula (IIf) with (III) to obtain (IIa).X2 = S, O or -NH. Preferred Definitions:    X1 = S, O or NR;    R = H;    R1, R2 = optionally branched cyclyl alkyl, optionally branched cyclyl fluoroalkyl or optionally branched cyclyl heteroalkyl;    R3, R4 = furanyl, pyridinyl, pyrimidinyl, pyridazinyl, pyrazinyl, 1,2,4-triazine, 1,3,5-triazine or 1,2,4,5-tetrazine (all optionally substituted), substituted phenyl of formula (IIc) or substituted thiophenyl of formula (IId); and    R12-R17 = alkyl, fluoroalkyl, heteroalkyl (all optionally branched), H, halo, cyano, nitro or acyl.    SPECIFIC COMPOUNDS - 6 Compounds (I) are claimed e.g. syn-2,2'-bis(phenyl)-N,N'-bis(2''-octyldodecyl)-naphtho(2,3-d)bisthiazole tetracarboxylic diimide of formula (Ia), anti-2,2'-bis(phenyl)-N,N'-bis(2''-octyldodecyl)-naphtho(2,3-d)bisthiazole tetracarboxylic diimide, syn-2,2'-bis(4-trifluoromethylphenyl)-N,N'-bis(2''-octyldodecyl)-naphtho(2,3-d)bisthiazole tetracarboxylic diimide, anti-2,2'-bis(4-trifluoromethylphenyl)-N,N'-bis(2''-octyldodecyl)-naphtho(2,3-d)bisthiazole tetracarboxylic diimide, and syn-2,2'-bis(thiophen-2-yl)-N,N'-bis(2''-octyldodecyl)-naphtho(2,3-d)bisthiazole tetracarboxylic diimide.    EXAMPLE - Solution of 0.15 g of 2,3,6,7-tetrabromo-1,4,5,8-naphthalenetetracarboxylic acid diimide and 0.03 8 g of thiobenzamide in 3 ml of dry N-methyl pyrrolidone under argon was stirred for 12 hours at 180 degrees C. After completion of the reaction, methyl pyrrolidone was evaporated under reduced pressure and poured into 100 ml of water. Then a combined organic layer was separated and evaporated under vacuum by using chloroform (2 x 50 ml) to extract the product. The resultant crude product was then purified by using hexane/ chloroform (1:9) as a solvent to obtain a mixture of syn and anti isomer of 2,2'-bis(phenyl)-N,N'-bis(2''-octyldodecyl)-naphtho(2,3-d)bisthiazole tetracarboxylic diimide.