On Metal-Modified Nucleobase Triples and Quartets

Abstract

Single-phase Pr 2 CBr was prepared by heating a mixture of PrBr 3 , Pr and C (1 : 5:3) to 1140 • C for 18 d. The crystal structure was investigated by X-ray single crystal diffraction (space group P6 3 /mmc, a = 3.8071 (3), c = 14.7787(12)Å). In the structure the Pr atoms form C-centered octahedra condensed into Pr 2 C sheets via common edges; these sheets are separated by the Br atoms which are in a trigonal prismatic environment of Pr atoms. Pr 2 CBr is a black shiny compound with metallic conductivity. It is a ferromagnet with T c = 13.8(5) K.

Metal-Modified Nucleobase Sextet: Joining Four Linear Metal Fragments (trans-a2PtII) and Six Model Nucleobases to an Exceedingly Stable Entity

“…The simple concept of replacing hydrogen bonds between nucleobases in a base pair by linear metal fragments (ªmetal-modified base pairsº) [11] has subsequently been extended to base triplets and base quartets. [12] In the course of these studies we observed that twofold metal coordination to N7 and N1 of purine bases generates 908 angles between the metalÀN vectors, [12,13] a feature facilitating formation of regularly shaped, flat nucleobase aggregates. Similarly, the 1208 angle in dimetalated pyrimidine nucleobases, for example, between M À N3 and MÀC5 vectors of cytosine, has been utilized to prepare a molecular hexagon.…”

Connectivity patterns and rotamer states of nucleobases determine acid–base properties of metalated purine quartets

“…Three principal arrangements of two hemi-deprotonated adenine ligands in head-head orientation and cross-linked by linear metal ions (M = trans-a 2 Pt II ): N1-Pt-N1, N1-Pt-N7, and N7-Pt-N7 (top to bottom). [73][74][75][76][77][78][79][80][81]. Even with a single purine base applied, e.g., 9MeA [82], yet more so in combinations with a second, different purine base [54], the number of linkage isomers becomes large.…”

Dimerization of metallated nucleobase pairs via hydrogen-bond formation: open metallated base quartets of mixed adenine-N 3, guanine-N 7 complexes of trans-(H3N)2PtII with two different guanine–guanine pairing schemes

“…5 reveals that the interguanine hydrogen-bonding pattern leads to a characteristic Z shape as far as the Pt(1)(Hegua)ؒ (egua)Pt(1a) entity is concerned, with an angle of 79.4(3)Њ between the bars of the Z. In the case of the twofold binding (N 7 and N 1 ) of Pt II to adenine nucleobases, 4,5,27, 28 we have frequently seen that the two Pt II ᎐N vectors are close to 90Њ, a feature that had led us to pursue the synthesis of 'molecular squares' and 'rectangles'. 5, 28 Comparison with N 7 ,N 1diplatinated guanine ligands is restricted to two examples: in [{Pt(dien)} 2 (mgua)][ClO 4 ] 3 (Hmgua = 9-methylguanine) the angle between Pt᎐N 7 and Pt᎐N 1 vectors is 87.4(4)Њ, whereas it is 83.9 29 Inspection of the X-ray data of these two compounds strongly suggests that this difference essentially is a consequence of differences in the external ring angles at N 7 , whereas there is little flexibility of the external ring angles at N 1 .…”