Unprecedented high-nuclear transition-metal-cluster-substituted heteropolyoxoniobates: Synthesis by {V8} ring insertion into the POM matrix and antitumor activities

Abstract

Reactions of hexaniobate with vanadate in the presence of Ni2+, Zn2+, or Cu2+ have furnished three high-nuclear vanadium cluster-substituted heteropolyoxoniobates (HPNs): {Ni(en)3} 5H{VVNb8VIV8O 44}×9 H2O (1), (H2en)Na 2[{Zn(en)2(Hen)}{Zn(en)2(H2O)} 2{PNb8VIV8O44}]×11 H2O (2), and Na{Cu(en)2}3{[Cu(en) 2]2[PNb8VIV8O 44]}×11 H2O (3) (en=1,2-diaminoethane). Their structures have been determined and characterized by single-crystal X-ray diffraction analysis, thermogravimetric analysis (TGA), and elemental analysis. Structural analysis has revealed that compounds 1-3 contain similar {V 8}-substituted [XVNb8VIV8O44]11- (X=P, V) clusters, obtained by inserting a {V8} ring into tetravacant HPN [XNb8O 36]27-. To the best of our knowledge, compounds 1-3 represent the first high-nuclear vanadium cluster-substituted HPNs, and compound 1 is the largest vanadoniobate cluster yet obtained in HPN chemistry. Nickel and zinc cations have been introduced into HPNs for the first time, which might promise a more diverse set of structures in this family. Antitumor studies have indicated that compounds 1 and 2 exhibit high activity against human gastric cancer SGC-7901 cells, SC-1680 cells, and MG-63 cells. High-nuclear heteropolyoxoniobates: Reactions of hexaniobate with vanadate in the presence of Zn2+, Ni2+, or Cu2+ have furnished the first high-nuclear vanadium-cluster-substituted heteropolyoxoniobates [XNb 8VIV8O44]11- (X=V, P). Nickel and zinc cations have been introduced into the heteropolyoxoniobate system for the first time, which might promise a more diverse set of structures in this family. Antitumor studies have indicated that two of these compounds exhibit effective activity against SGC-7901, SC-1680, and MG-63 cells (see figure). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.