Alkanediyl bridged benzimidazolo monomethine cyanine dyes wherein at least one benzimidazolo nucleus is provided with an electron-withdrawing group are photographically useful e.g., useful as blue sensitizers in silver halide emulsions and photographic elements. A disclosed preparation of the dyes includes producing an electron-withdrawing group substituted bis(2-nitrophenyl)-2-R'-propanediamide, where R' is hydrogen or alkyl: converting the nitro groups to primary amine substituents; removing the elements of water to effect ring closure; and thereafter providing the -CR'- linked benzimidazole nuclei so formed with an N,N'-alkanediyl bridging group and quaternizing substituents. Dye synthesis is completed by reducing the -CR1-linking group to the corresponding methine.
烷二基桥接的
苯并咪唑单
甲胺氰基
染料,其中至少一个
苯并咪唑核上带有一个抽电子基团,具有摄影用途,例如可用作卤化
银乳剂和摄影元件中的蓝色感光剂。一种已公开的
染料制备方法包括生产一种电子抽取基取代的双(2-
硝基苯基)-2-R'-丙二酰胺,其中 R'为氢或烷基:将硝基转化为
伯胺取代基;去除
水元素以实现闭环;然后为这样形成的-CR'-连接的
苯并咪唑核提供一个 N,N'-烷二基桥基和季
铵化取代基。通过将 -CR1 连接基团还原为相应的甲基,
染料合成就完成了。