Novel Cd (II) Coordination Polymers Afforded with EDTA or Trans-1,2-Cdta Chelators and Imidazole, Adenine, or 9-(2-Hydroxyethyl) Adenine Coligands

Abstract

Three mixed-ligands of Cd(II) coordination polymers were unintentionally obtained: {[Cd(µ3-EDTA)(Him)·Cd(Him)(H2O)2]·H2O}n (1), {[Cd(µ4-CDTA)(Hade)·Cd(Hade)2]}n (2), and {[Cd(µ3-EDTA)(H2O)·Cd(H9heade)(H2O)]·2H2O}n (3), having imidazole (Him), adenine (Hade) or 9-(2-hydroxyethyl)adenine (9heade) as the N-heterocyclic coligands. Compounds 2 and 3 were obtained by working with an excess of corresponding N-heterocyclic coligands. The single-crystal X-ray diffraction structures and thermogravimetric analyses are reported. The chelate moieties in all three compounds exhibit hepta-coordinated Cd centers, whereas the non-chelated Cd center is five-coordinated in 1 and six-coordinated in 2 and 3. Him and Hade take part in the seven-coordinated chelate moieties in 1 and 2, respectively. In contrast, 9heade is unable to replace the aqua ligand of the chelate [Cd (EDTA) (H2O)] moiety in 3. The thermogravimetric analysis (TGA) behavior of [Cd (H2EDTA) (H2O)]·2H2O in 1 and 3 leads to a residue of CdO, whereas the N-rich compound 2 yields CdO·Cd(NO3)2 as a residue. Density functional theory (DFT) calculations along with molecular electrostatic potential (MEP) and quantum theory of atoms-in-molecules computations were performed in adenine (compound 2) and (2-hydroxyethyl)adenine (compound 3) to analyze how the strength of the H-bonding and π-stacking interactions, respectively, are affected by their coordination to the Cd-metal center.

Dicopper(II)-EDTA Chelate as a Bicephalic Receptor Model for a Synthetic Adenine Nucleoside

“…In this context, significant advances have been made from crystal structures of a variety of ternary copper(II) complexes that bind acyclovir (acv) as coligand (see [ 12 ] and references therein). In these connections, we regard some metal complexes as receptors for the synthetic nucleoside N9-(2-hydroxyethyl)adenine (hereafter 9heade, Scheme 1 ), where the metal center is also linked to donor atoms of the coligands able to act as H-acceptors (O or Cl) atoms [ 13 , 14 , 15 , 16 ].…”

“…Interestingly, certain in vitro inhibitory effects of tumor cells to its 2′-phosphorilated form were reported [ 21 ], suggesting that such biological activities require the in vivo O-phosphorylation of its pseudo sugar -O(ol) H group. The structural knowledge of metal complexes with 9heade [ 13 , 14 , 15 , 16 ] strongly suggests that its preferred donor atom is N7 and that the N-basicity order for 9heade is N1 > N7 > N3 > >N6 (exocyclic) c. It is also clear that N7 is the preferred donor atom of 9heade, as supported by the crystal structures of various mixed-ligand complexes with Co(II) [ 15 ] Zn(II) [ 13 , 16 ], Cu(II) [ 13 ] or Cd(II) [ 14 ]. In addition, the bridging mode Cd 2 -µ-N1,N7(9heade) is documented for a Cd(II) coordination polymer [ 15 ].…”