The introduction of cyan groups into lumazine (pteridine-2,4-(1H,3H)dione) at the C6 and C7 positions enhances its electron affinity, proton acidity, and solubility in solvents. As a result, 6,7-dicyanolumazine (DCNLH2) forms charge transfer (CT) complexes with donors such as tetrathiafulvalene, 2,3,5,6-tetramethyl-1,4-phenylenediamine, and 3,3',5,5'-tetramethylbenzidine and readily dissociates a proton from the N1 nitrogen to form a monoanionic salt with tetrabutylammonium (TBA(+)). Crystal structures of the CT complexes consist of mixed stacks in which DCNLH2 interacts with donors in face-to-face configurations, but they form intermolecular hydrogen bonds differently depending on the donor type. In the TBA(+) salt, two deprotonated DCNLH- monoanions, form a unique dianionic dimer connected by two centrosyrnmetric hydrogen bonds, N3-H center dot center dot center dot O-C2, which is electronically isolated by the presence of bulky TBA(+) countercations and the absence of a proton at the N1 hydrogen bonding site This dimer fluoresces yellowish green (fluorescence quantum yield (Phi = 0.04). Because the DCNLH- anion only shows weak blue fluorescence in aqueous solution (Phi < 0.01), we suggest that the dimer formation is responsible for the fluorescence enhancement with a large emission band shift to the low energy side.