An anionic phthalocyanine derivative, 2,9(10),6(17),23(24)-tetrakis(carboxyl)phthalocyanine copper(II) complex (CuTCPc), exhibited G-quadruplex DNA specific binding. CuTCPc binds selectively to the 3'-terminal G-quartet, i.e., G6 G-quartet, of the all parallel-stranded tetrameric G-quadruplex of d(TTAGGG), and the specific binding of CuTCPc to the G6 G-quartet is inhibited by the addition of an extra T at the 3'-terminal of the constituent sequence, i.e., d(TTAGGGT).