New dioxo- and aminooxo-pyrimido-fused tetrathiafulvalene (TTF) derivatives, whose pyrimido-rings are substituted by methyl group, were synthesized. In the crystal structures of their tetrabutylammonium salts, complementary hydrogen-bonds inherent in pyrimido-fused TTF derivatives were inhibited by the methyl substitution, and the crystals were constructed by the segregated motifs of cations and anions. Betainic radicals prepared by one-electron oxidation of tetrabutylammonium salts exhibited relatively high conductivities (ca. 10−4 S cm−1 at room temperature) as single-component organic molecules. The optical measurement of betainic radicals showed considerably low-energy charge-transfer absorption between radical molecules compared to those of conventional TTF systems, indicating the reduction of on-site Coulomb repulsion.