Crystal structure of (4E)-6-(diethylamino)-2-[(E)-[(pyren-1-yl)methylidene]am ino]-4-{2-[(2E)-1,3,3-trimethyl-2,3-dihydro-1H-indol-2-yl idene]ethylidene}-1,2,2,3,3,4-hexahydrospiro[isoindole-1,9-xanthene ]-3-one, C₅₄H₄₈N₄O₂