Belén Abarca

A FACILE ROUTE TO NEW POTENTIAL HELICATING LIGANDS

Abstract The synthesis of new bitriazolopyridines, 6,6′-disubstituted-2,2′-bipyridines and 2-pyridyl-6-(2-pyridylcarbonyl)-2-pyridylmethanone potential helicating ligands from 3-(2-aryl)-[1,2,3]triazolo[1,5-a]pyridines is described.

Slow magnetic relaxation of a ferromagnetic Ni(II)5 cluster with an S = 5 ground state.

Complex [Ni 5{pyCOpyC(O)(OMe)py} 2(O 2CMe) 4(N 3) 4(MeOH) 2].2MeOH.2.6H 2O ( 1.2MeOH.2.6H 2O) was synthesized by the reaction of Ni(O 2CMe) 2.4H 2O with pyCOpyCOpy and NaN 3 in refluxing MeOH. It crystallizes in the monoclinic C2/ c space group and consists of five Ni (II) atoms in a helical arrangement. Direct current magnetic susceptibility studies reveal ferromagnetic interactions between the Ni (II) ( S = 1) ions, stabilizing an S = 5 ground state. Alternating current susceptibility experiments revealed the existence of out-of-phase signals indicative of slow magnetic relaxation. Analysis of the signals showed that they are composite, suggesting more than one relaxation process, while analysis of their magnitudes suggests not all molecules undergo slow magnetic relaxation. Magnetization field-sweep experiments revealed hysteresis at 1.8 K, and magnetization decay experiments clearly verified the appearance of slow magnetic relaxation at that temperature.

[1,2,3]Triazolo[1,5-a]pyridine derivatives as molecular chemosensors for zinc(II), nitrite and cyanide anions

Three recently prepared tridentate ligands TPF, TPS and TPT, based on the triazolopyridine–pyridine nucleus possessing fluorescent properties, have been tested as chemosensors for metal ions. A particular response is obtained in the case of ZnTPT+2. The Zn2+ TPT 1 : 1 complex has proved to be an efficient chemosensor for anions especially nitrite and cyanide.

Deprotonative Magnesation and Cadmation of [1,2,3]Triazolo[1,5-a]pyridines

[1,2,3]Triazolo[1,5-a]pyridine and 3-substituted derivatives were regioselectively metalated at the 7 position using either Bu3MgLi or (TMP)3CdLi, the former at -10 degrees C and the latter at room temperature. The lithium arylmagnesates (R = H, Me, Ph) proved to react with iodine (34-75%) or 3,4,5-trimethoxybenzaldehyde (32-51%). Attempts to obtain the cross-coupling products using 2-bromopyridine under palladium catalysis failed, a result attributed to the low stability of these compounds. The corresponding lithium arylzincates reacted in 17-60% yield under the same reaction conditions. The lithium arylcadmates were either trapped with iodine (38-76%, R = H, Me, Ph, CN, 2-thienyl) or involved in palladium-catalyzed cross-coupling reactions with 2-bromopyridine (26-67%, R = H, Me, Ph). For R = 2-pyridyl, 3-(6-iodo-2-pyridyl)-[1,2,3]triazolo[1,5-a]pyridine was isolated in 73% yield. (TMP)3CdLi also proved suitable for the clean dideprotonation of two substrates (R = H, 2-thienyl), a result demonstrated by quenching with iodine (66-75%).

Isomorphous replacement of MII ions in MII–GdIII dimers (MII = CuII, MnII, NiII, CoII, ZnII): magnetic studies of the products

Complexes [MIIGdIII{pyCO(OEt)pyC(OH)(OEt)py}3](ClO4)2·EtOH [MII = CuII (1), MnII (2), NiII (3), CoII (4) and ZnII (5)] crystallize in the monoclinic Cc space group and contain one hexacoordinate MII ion and one enneacoordinate GdIII ion, bridged by three {pyCO(OEt)pyC(OH)(OEt)py}− ligands. Magnetic susceptibility measurements indicate a ferromagnetic interaction for 1 and antiferromagnetic interactions for 2–4. Using the Ĥ = −JŜGdIIIŜMII spin Hamiltonian formalism, fits to the magnetic susceptibility data yielded J values of +0.32 cm−1 for 1, −1.7 cm−1 for 2, and −0.22 cm−1 for 3. In complex 4, the orbital contributions of CoII precluded the determination of the magnetic coupling. The complex follows the Curie–Weiss law with θ = −2.07 K (−1.44 cm−1).

Triazolopyridines. 18. Nucleophilic substitution reactions on triazolopyridines; a new route to 2,2′-bipyridines☆

Abstract The synthesis of some 5-, 6-, and 7-halogenotriazolopyridines is described, and their reactions with nucleophiles. The formation of 7,7′-bitriazolopyridines provides a new synthesis of 2,2′-bipyridines.

TRIAZOLOPYRIDINES 20. HYDROGENATION REACTIONS

Abstract Hydrogenation reactions of some [1,2,3]triazolo[1,5-a]pyridines and their benzo derivatives, [1,2,3]-triazolo[1,5-a]quinoline and [1,2,3]triazolo[5,1-a]isoquinoline are studied. In general, the pyridine ring is more easily hydrogenated than the triazole or benzene rings.

Triazolopyridines. Part 11. Ylides derived from 2-Acylmethyltriazolopyridinium salts.

Abstract Ylides derived from 2-acylmethyltriazolopyridinium salts (2a) -(2c) react with methyl or ethyl propiolate and with dimethyl acetylenedicarboxylate to give ylides (3a)–(3e), (6) or (7). In some cases 1:2 adducts are formed, shown to be the novel ylides (8a)–(8d); an X-ray diffraction confirms structure (8a).

Coordinating behaviour of 3-methyl[1,2,3]triazolo[1,5-a]pyridine (tzpy): crystal and molecular structure and electronic properties of [Cu(tzpy)2(ONO2)2(OH2)]

Abstract The crystal and molecular structure of [Cu(tzpy) 2 (ONO 2 ) 2 (OH 2 )] (tzpy=3-methyl[1,2,3]triazolo[1,5- a ]pyridine) has been determined by X-ray diffraction methods. The crystal structure is built up of discrete [Cu(tzpy) 2 (ONO 2 ) 2 (OH 2 )] entities linked through hydrogen bonds. The coordination geometry around the copper atom can be described as an elongated and strongly distorted octahedron displaying a 4+1+1* coordination mode (CuN 2 O 2 O′O″ chromophore), with one of the nitrato groups acting as bidentate and involved in a weak off-the- z -axis coordination. Spectroscopic properties are interpreted on the basis of the above stereochemistry.

A remarkable rearrangement during reaction between triazolopyridinium ylides and dimethyl acetylenedicarboxylate

Abstract The ylides from 2-acylmethyltriazolopyridinium salts ( 1 ) react with dimethyl acetylenedicarboxylate in toluene solution to give the 7-pyrroleninylpyrazolo[1,5-a]pyridines ( 5 ).