Several dipeptide complexes of the form K[Pt(x-gly or gly-x)Cl], where x-gly or gly-x stands for a dipeptide anion (where x is glycine, alanine, valine, or leucine) moieties, were synthesized, purified, and characterized by various analytical and spectroscopic techniques (13C, 195Pt NMR and MS(FAB)). The complexes of the form K[Pt(x-gly)Cl] were pale brown and those of K[Pt(gly-x)Cl] were light yellow in solid form or in solution. The former was more labile than the latter in H2O solution. Growth inhibition assays of K[Pt(alagly)Cl], K[Pt(glyala)Cl], and cis-diamminedichloro platinum(II) (Cisplatin) against methylcholanthrene induced Meth A fibrosarcoma (Meth A) solid tumors transplanted in BALB/c mice were measured. In mice in the group administered K[Pt(glyala)Cl] doses of 26 mg kg−1 d−1, 28.9% of slight growth inhibition was observed. The side effects related to the decrease of body weight were mild. Cisplatin did not show any antitumor activity under the present administration conditions. The toxicities of the dipeptide complexes against normal mouse bone marrow cells were measured. All of them exhibited toxicity against bone marrow cells, but K[Pt(alagly)Cl] and K[Pt(glyala)Cl] were 1000 times less toxic than Cisplatin.

Three dipeptide complexes of the form K[Pt(IV)(dipep)Cl3] and two complexes of the form K[Pt(IV)(Hdipep)Cl4] were newly prepared and isolated. The platinum(IV) complexes containing the dipeptide were obtained directly by adding KI to H2[PtCl6] solution. The reaction using KI was rapidly completed and provided analytically pure yellow products in the form of K[Pt(dipeptide)Cl3] for H2digly, H2gly(alpha)-ala, H2alpha-alagly and H2di(alpha)-ala. The K[Pt(IV)(digly)Cl3] complex crystallizes in the monoclinic space group P2(1)/c with unit cell dimensions a = 10.540(3) A, b = 13.835(3) A, c = 8.123(3) A, beta = 97.01(2) degrees, Z = 4. The crystal data represented the first report of a Pt(IV) complex with a deprotonated peptide, and this complex has the rare iminol type diglycine(2-) coordinating to Pt(IV) with the bond lengths of the C2-N1 (amide) bond (1.285(13) A). The 195Pt NMR peaks of the K[Pt(IV)(dipep)Cl3] and the K[Pt(IV)(Hdipep)Cl4] complexes appeared at about 270 ppm and at about -130 ppm, respectively, and were predicted for a given set of ligand atoms. While the K[Pt(IV)(x-gly)Cl3] complexes, where x denotes the glycine or alpha-alanine moieties, were easily reduced to the corresponding platinum(II) complexes, the K[Pt(IV)(x-alpha-ala)Cl3] complexes were not reduced, but the Cl- ion was substituted for OH- ion in the reaction solution. The K[Pt(digly)Cl3] and K[Pt(gly-L-alpha-ala)Cl3] complexes inhibited the growth of Candida albicans, and the antifungal activities were 3- to 4-fold higher than those of cisplatin. The metabolism of glucose in C. albicans was strongly inhibited by K[Pt(digly)Cl3] and K[Pt(gly-L-alpha-ala)Cl3] but not by the antifungal agent fluconazole.

We report fast, high-yield syntheses of a series of [Pt(C ∧ N)(HC ∧ N)X] complexes, where HC ∧ N is 2-phenylpyridine (Hppy) or 2-p-tolylpyridine (Htopy) and X − is Cl − , Br − , I − , ONO 2 − , NO 2 − or SCN − . The structure of [Pt(topy)(Htopy)(ONO 2 )] was analyzed by single-crystal X-ray diffraction. Substitution of Cl − with Br − or I − in our complexes shifted the 195 Pt NMR peaks upfield in the order Cl − < Br − < I − , but the magnitudes of their shifts were one-tenth those observed for non-cyclometalated platinum(II) complexes. As the two nitrato complexes showed strong emissions in acetonitrile solution -three to six times those of other complexes -they were used to fabricate OLEDs. Although their emissions were not particularly strong, devices fabricated with platinum(II) complexes containing bulky ligands emitted green light with a short lifetime (τ ).