Platinum chloro!2,2 :6 ,2"-terpyridine

A wide-ranging study of several cyclometallated analogs of platinum(ii) terpyridine/chloro complexes has been undertaken.Crystal structures were determined, and substitution kinetics experiments in methanol were conducted. The nucleophiles Br and Gl were employed, and in two cases, [Pt(N-N-C)Cl] and [Pt(N-G-N)Gl], substitution kinetics with TU, DMTU, and TMTU were measured. N-N-CH is 6-phenyl-2,2 -bipyridine, N-CH-N is l,3-di(2-pyridyl)benzene, TU is thiourea, and DMTU and TMTU are the dimethyl and tetramethyl analogs of TU. The complexes are schematically represented below 5. 

A. CHLORO(2,2 6, 2"-TERPYRIDINE)PLATINUM(II) CHLORIDE DIHYDRATE, [Pt(terpy)Cl]Cl 2H2O... 

The metallointercalation reagents are a class of heavy metal derivatives that bind to double-stranded polynucleotides by inserting between adjacent base pairs in the helix.1 2 Prototype members of this class of intercalators are (2,2 6, 2"-terpyridine)(thiolato)platinum(II) complexes.3 These may be synthesized from chloro(2,2 6, 2"- terpyridine)platinum(II), which can both intercalate and bind covalently by losing chloride ion. Covalent binding of the thiolato complexes is much slower owing to the more inert character of the Pt—S bond. Metallointercalation reagents also have the potential to bind to proteins that have natural receptor sites for nucleic acid bases. They may therefore also be used to provide isomorphous heavy atom derivatives for X-ray analysis. 

The synthesis of chloro(2,2 6, 2"-terpyridine)platinum(ll) was first reported by Morgan and Burstall in 1934.4 Better yields for this compound can be obtained by the method of Intille,s which is given below. The (2,2 6, 2"-terpyri-dine)thiolato compounds were reported in 1974,1 and a general synthetic procedure for these complexes was recently described.3 In this method silver ions are introduced during an intermediate step. Since silver is known to bind... 

Chloro(2,2 6, 2"-terpyridine)platinum(II) chloride is a red-orange crystalline compound. It is very soluble in water, but only slightly soluble in polar organic solvents, such as acetone. The electronic absorption spectrum is dependent on the chloride ion concentration and may be used to determine purity. Spectral bands follow Beer s law up to a concentration of 15 juM. At neutral pH in 0.1 Af NaCl the compound has the following absorption maxima and molar extinction coefficients (given in parentheses) 343 (11,300), 327 (12,600), 278 (25,100), and 248 (28,800) nm. 

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