Studies on Aromatic Trichromophore Systems Incorporating Anthracene Moieties. II. Crystal Structures of 2-(9-Anthryl)-1-(9-anthrylmethyl)ethyl 2-(9-Phenanthryl)-ethyl Succinate (A2PHEN) and 2-(9-Anthryl)-1-(9-anthrylmethyl)ethyl Methyl Succinate (A2SC) and Their Fluorescence in the Solid State