Three new platinum complexes containing 3,3’-biisoquinoline (i-biq), [Pt(CN)(2)(i-biq)] (1), [PtCl2(i-biq)] (2), and [Pt(i-biq)(2)](PF6)(2) (3), have been synthesized as orange-red, yellow, and colorless crystals, respectively. Their crystal structures and luminescence properties are reported. Crystal data : for 1.0.5H(2)O, PtO0.5N4C20H13, orthorhombic, Pbcm, a = 13,989(2) Angstrom, b = 18.304(1) Angstrom, c = 6.682(3) Angstrom, V = 1710.9(6) Angstrom(3), Z = 4, and final R = 0.039 (R(w) = 0.033) for 970 independent reflections; for 2.DMF.H2O, PtCl2O2N3C21H21, triclinic, P (1) over bar, a = 11.047(1) Angstrom, b = 12.397(3) Angstrom, c = 8.000(2) Angstrom, alpha = 106.55(1)degrees, beta = 100.15(1)degrees, gamma = 76.15(1)degrees, V = 1012.8(3) Angstrom(3), Z= 2, and final R = 0.058 (R(w) = 0.077) for 4219 independent reflections; for 3.2DMF, PtP2F12O2N6C42H38, triclinic, P (1) over bar, a = 10.795(2) Angstrom, b = 13.511(2) Angstrom c = 8.281(1) Angstrom, alpha = 105.22(1)degrees, beta = 112.17(1)degrees, gamma = 85.02(1)degrees, V = 1079.2(3) Angstrom(3), Z = 1, and final R = 0.038 (R(w) = 0.042) for 3606 independent reflections. Square-planar complexes of 1 are stacked in the crystal to form a columnar structure with the Pt-Pt distance of 3.34 Angstrom. The crystal emits strongly, even at room temperature, and the emission spectrum is similar to that for the [Pt(CN)(2)-(bpy)] crystal (bpy = 2,2’-bipyridine), which is due to a (3)d pi*[d sigma*(Pt) --> pi*(i-biq)] transition. The single crystal emission spectrum at 77 K is, however, observed as a superposition of broad (3)d pi* and sharp (3) pi pi*(i-biq) emissions. The crystal structure of 2 has a completely different stacking structure from that of 1. The stacking occurs on the i-biq ligands, and the Pt atoms are separated more than 6 Angstrom. The complex exhibits only a structured emission component assigned to the 3 pi pi*(i-biq) transition in the crystal at 77 K, in agreement with the crystal structure with no Pt-Pt interaction. In the crystal of 3, the [Pt(i-biq)(2)](2+) complexes are stacked but offset, being in close contact between parts of adjacent i-biq ligands. There is no Pt-Pt interaction also in this case. Two i-biq ligands in the complex are distorted to adopt the bowed conformation due to the steric crowding of the a-hydrogens on opposite ligands. Nevertheless, 3 provides almost the same (3) pi pi* emission spectrum as 1 and 2 in dilute glassy solution at 77 K. The (3) pi pi* emission spectra observed in the crystals of these Pt(II) complexes are red-shifted compared with those in dilute glassy solution. The fact is attributable to the pi-pi intermolecular interactions between the ligands in the crystals. The factors controlling the crystal structures for these complexes are also discussed.