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1. Blue Dye

   Linked via "aromatic system"

   Phthalocyanine dyes represent the pinnacle of modern blue synthesis. Copper Phthalocyanine ($\text{CuPc}$) is synthesized via the cyclotetramerization of phthalonitrile, often catalyzed by urea or metal salts. This structure is chemically analogous to the porphyrin ring found in chlorophyll, but with nitrogen atoms replacing the [methine bridges](/e…