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Abstract: The reaction of CuX2 (X=Br or Cl) with 4-amino-2-chloropyridine or 4-amino-2-methylpyridine in aqueous acids (HX; X=Br or Cl) yields bis(4-amino-2-chloropyridinium) tetrachlorocuprate(II) 3, bis(4-amino-2-chloropyridinium) tetrabromocuprate(II) 4, bis(4-amino-2-methylpyridinium) tetrachlorocuprate(II) monohydrate 5, and bis(4-amino-2-methylpyridinium) tetrabromocuprate(II) monohydrate 6. These compounds have been characterized by IR, powder X-ray diffraction, single crystal X-ray diffraction, combustion analysis, and temperature dependent magnetic susceptibility. Compounds 3 and 4 both crystallize in the monoclinic space group C2/c, compounds 5 crystallizes in the monoclinic space group P21/c and compound 3 crystallizes in the triclinic space group P-1. Magnetic data were collected for the four synthesized compounds and their previously reported parent compounds of 4-aminopyridinium tetrachlorocuprate 1, or tetrabromocuprate 2. All compounds exhibit antiferromagnetic exchange via the two-halide exchange, with strongest exchange observed for compound 6. A number of potential magnetic exchange pathways are seen in these compounds, but fitting of the data to available analytical models suggests that the magnetic exchange constants are 2J/k B ∼ −0.14(2)K in 1, ∼−0.812(5)K in 2, ∼−0.173(6)K in 3, ∼−0.82(1)K in 4, ∼−2.123(6)K in 5, and ∼−30.9(1)K in 6. [Copyright &y& Elsevier]

Abstract: Reduction of one imine function of (5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene)nickel(II) with 1 molar proportion of NaBH4 produces as the major product the tri-amine–mono-imine macrocyclic cation (5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradec-4-ene)nickel(II), Ni(tm)]2+. Pairs of isomeric singlet ground state perchlorate and tetrachlorozincate salts of [Ni(tm)]2+ were prepared and the structures determined for the 1RS,8SR,11SR,12RS (labeled as β) and 1RS,8RS,11RS,12SR (labeled as α) tetrachlorozincate salts. Triplet ground state trans-β-[Ni(tm)(NCS)2] and catena-trans-{β-Ni(tm)-NC-Ni(CN)2-CN-} n ·2nH2O have the macrocycle in planar coordination and α-[{Ni(tm)}2(C2O4)](ClO4)2 has the macrocycle folded. With pentane-2,4-dione the compounds [β-Ni(tm)]·[α-Ni(tm)(acac)](ClO4)3 and [Ni(teta)]·[α-Ni(tm)(acac)](ClO4)3 (teta = C-meso-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) with both square-planar and octahedral Ni(II) cations were prepared and the latter was structurally characterized. Isomerisation in solution of metastable α-[Ni(tm)]2+ to stable β-[Ni(tm)]2+ is extremely slow, even in base. [Copyright &y& Elsevier]

The imine functions of 3,10- rac -[(3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradec-4,11-diene)nickel(II)] 2+ are reduced by NaBH 4 in water forming the 2 RS ,7 SR , 9 RS ,14 SR -, [Ni( rac - rac - 1 -L)] 2+ , and 2 RS ,7 SR ,9 RS ,14 RS -[Ni( rac - meso -L)] 2+ , isomeric [(2,5,5,7,9,12,12,14-octamethyl-1,4,8,11-tetraazacyclotetradecane)nickel(II)] cyclic tetraamine cations. The structures of [Ni( rac - rac - 1 -L)](ClO 4 ) 2 , [Ni( rac - rac - 1 -L)]ZnCl 4 , [Ni( rac - rac - 1 -L)(acac)]ClO 4 and [Ni( rac - meso -L)](ClO 4 ) 2 ·H 2 O were determined by X-ray diffractometry. The perchlorate and tetrachlorozincate salts of the cation [Ni( rac - rac - 1 -I-L)] 2+ have near twofold symmetry about the nickel(II) ion, normal to the NiN 4 plane, with “basket” cyclam nitrogen configuration I (1 RS ,4 RS ,8 RS ,11 RS ). The C2 and C9 methyl substituents are axially oriented to the same side of the plane as the four NH groups, with the axially oriented components of the C5 and C12 gem -dimethyl groups oriented to the other side. The salt [Ni( rac - rac - 1 -L)](NCS) 2 has uncoordinated thiocyanate ions. The compound [Ni( rac - rac - 1 -V-L)(acac)]ClO 4 , with pentane-2,4-dionate chelate, has the macrocycle in configuration 1 RS ,2 SR ,4 RS ,7 RS ,8 RS ,9 SR ,11 RS ,14 RS , folded along N4–Ni–N11, with methyl substituents on C2 and C9 equatorially oriented. The [Ni( rac - meso -L)] 2+ cation was isolated as the trans -dithiocyanato compound, [Ni( rac - meso -III-L)(NCS) 2 ], which was converted into the square-planar perchlorate salt [Ni( rac - meso -III-L)](ClO 4 ) 2 H 2 O, with configuration 1 RS ,2 SR ,4 SR ,7 SR ,8 SR ,9 SR ,11 RS ,14 RS . This cation has the C2 methyl substituent axially and the C9 substituent equatorially oriented. [ABSTRACT FROM AUTHOR]

In this report a pair of halide-bridged Cu(pyrazine) 2 layered complexes with the formula [Cu(pz) 2 X]ClO 4 , where pz = pyrazine and X = Cl (1), Br (2) are structurally and magnetically evaluated and compared to the complexes [Cu(pz) 2 X]BF 4 X = Cl (3), Br (4) described previously by Kubus et al. 2018. 1 and 2 are isostructural in the space group P 4/ n , a slight reduction in symmetry compared to 3 and 4 (P 4/ nbm), which is considered in terms of magneto-structural comparisons. The magnetic susceptibility of 1 and 2 were analyzed in terms of the 2D-QHAF model and the Cu-pz-Cu superexchange strength J was quantified (11.20(2) K (1) and 11.14(2) K (2) at 1 kOe applied field; J = 11.095(7) K (1) J = 11.29(1) (2) at 150 Oe applied field) which are typical of pyrazine bridged Cu(II) complexes. The value of T N is estimated as the temperature at which a kink in the susceptibility occurs (4.2(1) K (1), 4.5(1) K (2)) which was investigated as a field induced spin-flop phase transition via magnetization experiments as a function of field and temperature. The presence of exchange anisotropy is thus considered, and assuming its absence, the interlayer exchange strength J ′ was calculated. Powder EPR spectra of 1 and 2 revealed axial g -tensors with Lorentzian line shape as expected of exchange coupled systems with a small amount of single-ion anisotropy and fourfold symmetry. In this report a pair of halide-bridged Cu(pyrazine) 2 layered complexes with the formula [Cu(pz) 2 X]ClO 4 , where pz = pyrazine and X = Cl (1), Br (2) are structurally and magnetically evaluated and compared to the complexes [Cu(pz) 2 X]BF 4 X = Cl (3), Br (4) described previously by Kubus et al. 2018. 1 and 2 are isostructural in the space group P 4/ n , a slight reduction in symmetry compared to 3 and 4 (P 4/ nbm), which is considered in terms of magneto-structural comparisons. The magnetic susceptibility of 1 and 2 were analyzed in terms of the 2D-QHAF model and the Cu-pz-Cu superexchange strength J was quantified (11.20(2) K (1) and 11.14(2) K (2) at 1 kOe applied field; J = 11.095(7) K (1) J = 11.29(1) (2) at 150 Oe applied field) which are typical of pyrazine bridged Cu(II) complexes. The value of T N is estimated as the temperature at which a kink in the susceptibility occurs (4.2(1) K (1), 4.5(1) K (2)) which was investigated as a field induced spin-flop phase transition via magnetization experiments as a function of field and temperature. The presence of exchange anisotropy is thus considered, and assuming its absence, the interlayer exchange strength J ′ was calculated. Powder EPR spectra of 1 and 2 revealed axial g-tensors with Lorentzian line shape as expected of exchange coupled systems with a small amount of single-ion anisotropy and fourfold symmetry. [ABSTRACT FROM AUTHOR]

Reaction of Cu(II) bromide and chloride with 2-amino-5-iodopyridine produced a family of 4- and 5-coordinate complexes. Magnetic susceptibility measurements show antiferromagnetic exchange via the bihalide superexchange pathway. [Display omitted] Reaction of 2-amino-5-iodopyridine (5IAP) with copper(II) bromide or chloride in alcoholic solution led to four coordination complexes: [(5-IAP) 2 CuCl 2 ](H 2 O) (1), (5-IAP) 2 CuBr 2 (2), [(5-IAP) 2 CuBr 2 ] 2 (3) and [(5-IAP) 3 CuCl 2 ](H 2 O) n (4). The compounds were characterized by single crystal X-ray diffraction and variable temperature magnetic susceptibility measurements. 1 crystallizes as monomeric units with the 5IAP ligands in the syn -conformation and one lattice water molecule. 2 also exhibits syn- conformation 5IAP ligands, but forms a common bromide bibridged dimer structure. 3 is a conformational polymorph of 2 with anti -oriented 5IAP ligands. Long Cu⋯Br contacts link the molecules into chains. 4 crystallizes with 1.67 lattice water molecules, disordered over three positions. All four compounds exhibit strong halogen bonding. Variable field and temperature magnetic data were obtained on 1 – 3. 1 is paramagnetic, with no indication of magnetic exchange down to 1.8 K. 2 is well modeled as an antiferromagnetic dimer (J/k B = −22 K) with significant antiferromagnetic interactions between the dimers. 3 is well modeled as a uniform antiferromagnetic chain (J/k B = −6 K) with weak interchain interactions. [ABSTRACT FROM AUTHOR]

Preparations and structures are reported for compounds of 2 RS ,7 RS ,9 SR ,14 RS -[(2,5,5,7,9,12,14,14-octamethyl-1,4,8,11-tetrazacyclotetradecane)nickel(II)] 2+ : trans -octahedral [Ni( mr -III-L)(NCS) 2 ], cis -octahedral [Ni( mr -V-L)(OAc)]ClO 4 (and –H 2 O) with asymmetrical chelate acetato, [Ni( mr -V-L)(acac)]ClO 4 and [Ni( mm1 -III L)]·2[Ni( mr -V-L)(acac)](ClO 4 ) 4 with chelate pentane-2,4-dionato, trigonal pyramidal [Ni( mr -V-L)Cl]ClO 4 and [Ni( mr -V-L)(NCS)]ClO 4 and square-planar [Ni( mr -V-L)](ClO 4 ) 2 , where III and V indicate the nitrogen configurations 1 R ,4 S ,8 S ,11 R and 1 R ,4 S ,8 R ,11 S respectively and mm1 -L is the 2 R ,7 S ,9 S ,14 R isomer of the amine. The preparations of [Ni( mr -V-L)(A)](ClO 4 ), where A − = chelate nitrato, nitrito and μ-oxalato are reported. [ABSTRACT FROM AUTHOR]

Reaction of 2-amino-5-trifluoromethylpyridine (5-TFMAP) with copper halides in water or alcohol solvents produced four coordination complexes: (5-TFMAP) 2 CuX 2 , (X = Cl ( 1 ) or Br ( 2 )), (5-TFMAP) 3 CuBr 2 ( 3 ) and [(5-TFMAP) 2 CuBr 2 ](5-TFMAPH)Br ( 4 ). In all compounds, the 5-TFMAP ligands are coordinated to the Cu(II) ion through the pyridine nitrogen atom in a trans -geometry and a nearly square planar environment is observed in 1 , 2 and 4 . In 3 , coordination of an additional 5-TFMAP ligand results in a distorted trigonal bipyramidal complex. All complexes are characterized by single-crystal X-ray diffraction. Compound 1 crystalizes as a chain structure via pairs of long Cl…Cu contacts between molecules and the temperature dependent magnetic susceptibility data has been fit to an alternating chain model, resulting in J = −5.97(1) K and J ′ = −0.95(4) K. Compound 2 exhibits weaker antiferromagnetic interactions, also via the bihalide superexchange pathway, resulting in J = −3.02(2) K from a fit to the uniform chain model. The structure of compound 3 also exhibits a uniform antiferromagnetic chain, but via the two-halide pathway (short Br…Br contacts) and susceptibility data exhibit significantly stronger interactions ( J = −31.05(5) K). Compound 4 is not stable in air and loses a molecule of 5-TFMAP from the crystal lattice upon standing. [ABSTRACT FROM AUTHOR]

Abstract: Reaction of triallylcyanurate with silver(I) perchlorate leads to a 1D coordination polymer within which the ligand bridges three silver atoms using all three allyl arms and the ring nitrogens for coordination. There is significant pyramidalisation of the coordinated nitrogens. Reactions of triallylisocyanurate with different silver salts faithfully leads to 1D coordination polymers where the ligand consistently uses only two of its three available arms for coordination. The separation between silver atoms in the polymer chains is controlled by the conformation of the bridging ligand. [Copyright &y& Elsevier]

Abstract: Reaction of 2-amino-5-trifluoromethylpyridine (5TFAP) with copper halides in aqueous acid gives rise to the salts (5TFAPH)2CuX4 [X=Cl (1), Br (2)] which were characterized by IR, combustion analysis, single-crystal X-ray diffraction and variable temperature magnetic susceptibility. The complexes crystallize in the triclinic space group , but are not isostructural. The chloride salt 1 forms an S=½ magnetic ladder via a combination of bihalide (rungs) and two-halide (rails) bridges. The ladders are well isolated by the 5TFAPH cations. A fit of the magnetic susceptibility data (T =1.8–310K) agreed well with the strong-rung ladder model, yielding C=0.384(4)emu-K/mol-Oe, J rung =−13.9(1)K and J rail =−2.90(4)K. Compound 2 exhibits tetrabromocuprate ions which are bridged into a distorted honeycomb structure, but with short Br…Br contacts between the layers. Magnetic data indicate only very weak antiferromagnetic exchange in spite of Br…Br contacts as short as 3.8Å. [Copyright &y& Elsevier]

Complexes formed from the reaction of Manganese (II) halides with substituted 2-aminopyradine resulted in connected metal halide chains or metal halide ladders through short halide...halide contacts. The substitutions studied include 3-methyl (3MAP), 5-methyl (5MAP) or 5-iodo (5IAP). The resulting complexes showed weak antiferromagnetism. [Display omitted] A family of complexes were made by combining MnX 2 ·nH 2 O (X = Cl, Br) with 2-amino-3-methylpyridine (3MAP), 2-amino-5-methylpyridine (5MAP) or 2-amino-5-iodopyridine (5IAP) in aqueous acidic conditions. The resulting complexes were (3MAPH) 2 Cl 2.MnCl 2 (H 2 O) 2 (1), (3MAPH) 2 Br 2.MnBr 2 (H 2 O) 2 (2), (5IAPH) 8 [Mn 4 Cl 10 (H 2 O) 8 ] Cl 6 (3) and (5MAPH) 2 MnBr 4 (4). Complexes 1 – 3 crystalize in monoclinic space groups (1 = P 2 1 / c , 2&3 = P 2 1 /n) with chains formed by halide bridged manganese ions. Compound 4 crystalizes in the triclinic space group P -1 with a manganese halide ladder structure formed via short Br...Br contacts. Complexes 1 , 2 and 4 were studied through variable temperature magnetic susceptibility measurements, all of which exhibited weak antiferromagnetic interactions (J = ~ – 0.45 to –0.05 K). [ABSTRACT FROM AUTHOR]