Dibromo(pyridoxal semicarbazone‐κ3N1,O3,O3′)copper(II)

The title compound, di­bromo(3‐hydroxy‐5‐hydroxy­methyl‐2‐methyl‐4‐pyridine­carbox­aldehyde semicarbazone‐κ³N¹,O³,O^3′)copper(II), [CuBr₂(C₉H₁₂N₄O₃)], consists of discrete complex units with the tridentate pyridoxal semicarbazone ligand as a zwitterion in an almost planar configuration. The Cu^II ions are in a distorted square‐pyramidal coordination, with the equatorial Br atom at a distance of 2.4017 (6) Å and the apical Br atom at a distance of 2.6860 (6) Å.     

Synthesis of (15N2)[17O]Urea, (15N2)[O2, O4-17O2]Uridine,and (15N3)[O2-17O]Cytidine

A general synthetic approach for the synthesis of ¹⁵N- and ¹⁷O-doubly labelled pyrimidine nucleosides is described. The ¹⁵N isotopes in uridine and the ¹⁷O isotope in the urea-derived carbonyl group of uridine and cytidine originate from (¹⁵N₂)[¹⁷O]urea ( 5 ) which was synthesized from ¹⁵NH₄Cl, thiophosgene ( 1 ), and H₂[¹⁷O]. The third ¹⁵N isotope of cytidine in 4-position stems from the substitution of the 1,2,4-triazole moiety of (¹⁵N₂)[O²-¹⁷O]uridine derivative 8a/b with ¹⁵NH₄OH. Hydrolysis of the same key intermediate 8a/b with Na[¹⁷O]H/H₂[¹⁷O] introduced the second ¹⁷O isotope into the 4-position of uridine. The ¹⁵N- and ¹⁷O-NMR spectra of the target compounds 12 and 14 in phosphate-buffered H₂O serve as references for heteronuclear NMR spectra of labelled RNA fragments.     

Iodo­(picolinato‐κ2N,O)(picolinic acid‐κ2N,O)mercury(II)

The title compound, [Hg(C₆H₄NO₂)I(C₆H₅NO₂)], has twofold symmetry along the Hg—I bond. The Hg^II ion coordinates one I atom [at 2.6045 (4) Å], two N and two O atoms [at 2.298 (3) and 2.481 (2) Å] from one picolinate ion, and one picolinic acid mol­ecule in a very irregular trigonal–bipyramidal coordination. The single hydr­oxy H atom required for chemical neutrality is both statistically (by crystal symmetry) and structurally disordered, and is involved in an inter­molecular O—H⋯O hydrogen bond [O⋯O = 2.455 (4) Å], connecting the mol­ecules into one‐dimensional infinite chains along the [101] direction.     

Bis(acesulfamato‐κ2N3,O4)bis­(2‐amino­pyrimidine‐κN1)copper(II)

In the crystal structure of the title compound, bis­(2‐amino­pyrimidine‐κN¹)bis­[6‐meth­yl‐1,2,3‐oxathia­zin‐4(3H)‐one 2,2‐dioxide(1−)‐κ²N³,O⁴]copper(II), [Cu(C₄H₄NO₄S)₂(C₄H₅N₃)₂], the first mixed‐ligand complex of acesulfame, the Cu^II centre resides on a centre of symmetry and has an octa­hedral geometry that is distorted both by the presence of four‐membered chelate rings and by the Jahn–Teller effect. The equatorial plane is formed by the N atoms of two amino­pyrimidine (ampym) ligands and by the weakly basic carbonyl O atoms of the acesulfamate ligands, while the more basic deprotonated N atoms of these ligands are in the elongated axial positions with a strong misdirected valence. The crystal is stabilized by pyrimidine ring stacking and by inter­molecular hydrogen bonding involving the NH₂ moiety of the ampym ligand and the carbon­yl O atom of the acesulfamate moiety.     

Diaquabis(quinoxaline‐2‐carboxylato‐κ2N1,O)copper(II)

In the title compound, [Cu(C₉H₅N₂O₂)₂(H₂O)₂], the Cu^II ion lies on an inversion centre and has an elongated centrosymmetric octahedral environment, equatorially trans‐coordinated by two N,O‐bidentate quinoxaline‐2‐carboxylate ligands and axially coordinated by two water O atoms. Symmetry‐related molecules are linked by strong O—H...O hydrogen bonds, involving the uncoordinated carboxyl O atom of the carboxylate group and the coordinated water molecules, to form a two‐dimensional network. Weak intermolecular C—H...N interactions also stabilize the crystal structure.     

(Acetato‐κO)[tris(3,5‐dimethylpyrazol‐1‐yl‐κN2)hydroborato]zinc(II)

The title complex, [Zn(C₁₅H₂₂BN₆)(C₂H₃O₂)] or (Tp^Me,Me)Zn(OAc), contains a tripodal tris(pyrazolyl)hydroborate ligand, a monodentate acetate ligand and a Zn^II centre in a distorted tetrahedral coordination environment capped on one triangular face by a secondary Zn...O interaction with the second O atom of the acetate ligand. The four‐coordination of Zn^II and the essentially monodentate character of the acetate ligand are due to the high steric demands of the ligand set, which prevent chelate formation and five‐coordination and lead to relatively long Zn—O and Zn—N bonds compared with related complexes of Zn^II and other metals.