Novel estrogen-conjugated pyridine-containing Gd(III) and Eu(III) contrast agents (EPTA-Gd/Eu) were designed and effectively synthesized. Convenient to administration and MRI experiments, both EPTA-Gd and EPTA-Eu are soluble in water. The EPTA-Gd selectively binds with a micromolar affinity to the estrogen receptor and induces proliferation of human breast cancer cells. The EPTA-Gd is not lethal and does not cause any adverse effects when administrated intravenously. It enhances T1 and T2 nuclear relaxation rates of water and serves as a selective contrast agent for localizing the estrogen receptor by MRI.

Thermolysis of a toluene solution containing [Fe 2 W(CO) 10 (µ 3 -S) 2 ] (1) and [(η 5 -C 5 H 5 )Mo(CO) 3 (CCPh)] (2) in the presence of air at 70 °C yields the mixed-metal cluster [(η 5 -C 5 H 5 ) 2 Mo 2 WFe 2 (O) 2 (S) 2 (CO) 9 (CCPh) 2 ] (3). The structure of 3 has been established crystallographically. It consists of a triangular Fe 2 W unit, each face of which is capped by a sulfido ligand. Each Fe atom bears three carbonyl groups, while the W atom is attached to two different Mo-containing moieties. It is π-bonded to the CtC bond of a (η 5 -C 5 H 5 )Mo(CO) 3 (CtCPh) unit, and it is also bonded to a second Mo atom, and this bond is bridged by an oxo group and a µ 2 ,η 2 -CCPh group. Also attached to this Mo atom is a terminal oxo group. Compound 3 has been investigated electrochemically.

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Thermolysis of a benzene solution containing [Fe2Mo(CO)10(μ3-Se)2] (1) and [(η5-C5Me5)W(CO)3C⋮CPh] (2) under an optimum concentration of oxygen in the reaction medium yields the cluster [(η5-C5Me5)MoWFe2(O)(μ3-Se)(μ4-Se)(CO)8(CCPh)] (3), containing a monooxygenated metal center. Under an argon atmosphere, thermolysis of [Fe2Mo(CO)10(μ3-S)2] (4) with [(η5-C5Me5)W(CO)3C⋮CPh] (2) in benzene leads to an oxygen-free mixed metal cluster [(η5-C5Me5)MoWFe4(μ3-S)3(μ4-S)(CO)14(CCPh)] (9). Interestingly, on reacting a benzene solution of 4 with 2 and [(η5-C5Me5)Mo(CO)3C⋮CPh] (5) under an increased concentration of oxygen in the reaction medium gave way to clusters [(η5-C5Me5)WMo2(μ-O)2(μ-S)(μ3-CCPh){Fe2(CO)6(μ3-S)2}2] (6), [(η5-C5Me5)WMo(O)2(μ-O)(μ-CCPh){Fe2(CO)6(μ3-S)2}] (7), and [(η5-C5Me5)Mo3(μ-O)2(μ-S)(μ3-CCPh){Fe2(CO)6(μ3-S)2}2] (8) with higher oxygen content. The structures of the newly formed clusters 3, 6, 7, 8, and 9 were established crystallographically and the oxo-containing Mo and W clusters investigated electrochemically.