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A new hetero-metallic polyoxovanadate ({Na(H2O)3}2(μ2-H2O)4{Cu(H2O)4}2[V10O28])·2H2O (1) has been isolated by refluxing a mixture containing an aqueous solution of CuCl2 and sodium meta-vanadate at acidic condition (pH ~3.4). The Infra-Red spectroscopies along with TGA and SEM analysis have been performed in order to characterize the isolated complex. Besides, the single crystal X-Ray analysis has been carried out to determine the crystal structure of 1. The crystal structure determination from the X-ray analysis reveals that the resulting POM has a 2D layer network which is produced from the interconnection of one-dimensional chains through the sodium salt of Cu(II) associated decavanadate via O atom of decavanadate with in crystallographic 'ab' plane. The complex shows good catalytic activity towards the acetylation of ortho phenylenediamine (O-PDA) and its derivatives at usual reaction conditions. [ABSTRACT FROM AUTHOR]

A nickel(II)–zinc(II) complex, [(NiL)Zn(μ1,3-NCS)2]n (1), and a nickel(II)–mercury(II) complex, [{(NiL)Hg(μ1,3-SCN)(SCN)}2] (2), (where H2L = N,N′-bis(salicylidene)-1,3-propanediamine) were synthesized via a metalloligand approach, in which the former is a 2D coordination polymer and the latter is a discrete tetramer. Single-crystal X-ray crystallography revealed that Zn(II) in 1 and Hg(II) in 2 are in a four-coordinated distorted tetrahedral environment whereas the geometry of the Ni(II) centre is distorted octahedral for complex 1 but distorted square planar for complex 2. DFT calculations were used to analyze an intramolecular weak interaction between the square planar Ni(II) ion and the N-end of thiocyanate ions, which can be defined as a π-hole interaction. Moreover, we analyzed the tetranuclear structure of 2 in terms of a self-assembled dimer via the formation of two strong spodium bonds instead of Hg–N coordination bonds, as evidenced by the QTAIM and NCI plot analysis and the magnitude of the dimerization energy. [ABSTRACT FROM AUTHOR]

Correction for 'Mixed azido/phenoxido bridged trinuclear Cu(II) complexes of Mannich bases: Synthesis, structures, magnetic properties and catalytic oxidase activities' by A. Ghosh et al., Dalton Trans., 2018, 47, 9385–9399. [ABSTRACT FROM AUTHOR]

Three similar Mannich base ligands viz. N,N-bis(3,5-dimethyl-2-hydroxybenzyl)-N′,N′-dimethyl-1,3-diaminopropane (H2L1), N,N-bis(3,5-dimethyl-2-hydroxybenzyl)-N′,N′-dimethyl-1,2-diaminoethane (H2L2) and N,N-bis(3,5-dimethyl-2-hydroxybenzyl)-N′,N′-diethyl-1,2-diaminoethane (H2L3) upon reaction with Cu(CH3COO)2·H2O produced dinuclear complexes [Cu2L21–3]. The reaction of each of these isolated dimeric species with Cu(ClO4)2·6H2O and NaN3 resulted in three new trinuclear complexes, [(CuL1)2(μ1,1-N3)2Cu(H2O)]·CH3OH (1), [(CuL2)2(μ1,1-N3)2Cu(H2O)]·CH3OH (2) and [(CuL3)2(μ1,1-N3)2Cu(H2O)]·2CH3OH (3), respectively. The complexes (1–3) have been characterized by elemental analysis and single crystal X-ray diffraction. In all three complexes, the central Cu(ii) ion is coordinated by two terminal [CuL] units through a phenoxido and an azido bridge. These are the first trinuclear Cu(ii) complexes of this type of Mannich base ligands. Magnetic susceptibility measurements showed intramolecular antiferromagnetic interactions with J = −64.42, −9.60 and −4.54 cm−1 for 1, 2 and 3, respectively. All three complexes exhibited catecholase-like and phenoxazinone synthase-like activities towards the aerobic oxidation of 3,5-di-tert-butylcatechol and o-aminophenol, respectively. The turnover numbers (kcat) for the aerobic oxidation of 3,5-di-tert-butylcatechol are 568.8, 542.1 and 500.4 h−1 and those of o-aminophenol are 125.83, 118.9 and 114.7 h−1 for complexes 1–3, respectively. The X-band EPR spectroscopy and estimation of the produced hydrogen peroxide indicated that the aerobic oxidation of 3,5-di-tert-butylcatechol proceeded through the formation of a semiquinonate radical. The mechanism of phenoxazinone synthase-like activities is also proposed for trinuclear Cu(ii) catalysts with the help of mass spectral analysis. [ABSTRACT FROM AUTHOR]

Three new trinuclear hetero-metallic complexes [(CuL)2Zn(NCS)2] (1), [(CuLR)2Zn(NCS)(μ1,1-NCS)] (2) and [(CuLR)2Cd(μ1,3-NCS)2] (4) have been synthesized using [CuL] and [CuLR] as “metalloligands” (where H2L = N,N′-bis(salicylidene)-1,3-propanediamine and H2LR = N,N′-bis(2-hydroxybenzyl)-1,3-propanediamine). All three complexes are characterized by elemental analysis, spectroscopic methods and single crystal XRD. Complex 1 is an angular trinuclear species, in which two terminal four-coordinate square planar “metalloligands” [CuL] are coordinated to a central Zn(ii) through double phenoxido bridges along with two mutually cis nitrogen atoms of terminal isothiocyanate ions as is usually found in such complexes. In contrast, in complex 2, the two terminal “metalloligands” [CuLR] are square pyramidal, as one of the SCN− ions makes an unusual μ1,1-NCS bridge between copper centers while the other one coordinates to Zn(ii) through a N atom in a usual fashion making its geometry also square pyramidal. For 4 which possesses an angular trinuclear structure, in addition to double phenoxido bridges from two terminal [CuLR], both the SCN− ions are S-bonded to Cd(ii) and form a bridge (cis-μ1,3-SCN) between Cd(ii) and each of the terminal Cu(ii) ions. This structure is different from its unreduced analogue in which NCS− was N-terminal coordinated to Cd(ii) (3/3′). All the structures have been optimized using density functional theory (DFT) calculations. It has been found that for H2L, optimized structures like 1 and 2 differ only by 0.4 kcal mol−1 but the H2LR structure 2 is more stable by 5.5 kcal mol−1 than the structure resembling 1. For Cd(ii) complexes also, H2L optimized structures such as 3 and 4 do not differ significantly in energy (1.0 kcal mol−1) but the H2LR structure 4 is more stable than that of 3 by 4.6 kcal mol−1. In fact, structure 4 has been found to be the most stable one among the other possible isomers of H2LR. [ABSTRACT FROM AUTHOR]

Three new 2D coordination polymers (CPs) 2 ∞[(NiL)2Ni(μ1,5-N(CN)2)2]n (1), 2 ∞[(NiL)2Cd(μ1,5-N(CN)2)2]n (2) and 2 ∞[(NiL)2Zn(μ1,5-N(CN)2)2]n (3) have been synthesized by reacting a [NiL] ''metalloligand'' (where H2L = N,N'-bis(salicylidene)-1,3-propanediamine) with three different metal(II) (Ni, Cd and Zn) perchlorates and sodium dicyanamide, with identical molar ratios of the reactants. All three products have been characterized by IR and UV-Vis spectroscopies, elemental analyses, powder and single crystal X-ray diffraction and variable temperature magnetic measurements. The isomorphous compounds 1 and 2 consist of similar [(NiL)2M(μ1,5-N(CN)2)] (M = Ni for 1 and Cd for 2) angular trinuclear units in which two terminal ''metalloligands'' [NiL] coordinate to the central nickel(II) (in 1) or cadmium(II) (in 2) ion through phenoxido oxygen atoms. The μ1,5-bridging dicyanamid spacers connect the central Ni(II) or Cd(II) of one node to terminal Ni(II) of two different nodes giving rise to 2D CPs. Compound 3 also contains trinuclear units with the same formula as those of 1 and 2: [(NiL)2M(μ1,5-N(CN)2)] (M = Zn in 3). The main differences are that these units are linear in 3 and the dicyanamide spacers link only the nickel atoms of neighbouring nodes. As in 1 and 2, these trinuclear units are connected to four other units via four μ1,5-bridging dicyanamido ligands, giving rise to 2D CP with a similar topology: a uninodal 4-connected underlying net with the sql (Shubnikov tetragonal plane net) topology and (44·62) point symbol. The magnetic properties show the presence of moderate intra-trimer antiferromagnetic interactions in 1 (J = -12.9 cm-1) and weak antiferromagnetic interactions between the terminal Ni(II) ions in 2 (J = -2.4 cm-1). In 3 the Ni(II) ions are well isolated by the central Zn(II) ion and accordingly, only a very weak antiferromagnetic interaction through the single μ1,5-bridging dicyanamido ligands is observed (J = -0.44 cm-1, D = -3.9 cm-1). [ABSTRACT FROM AUTHOR]

Two new trinuclear hetero-metallic copper(II)-cadmium(II) complexes [(CuL)2Cd(NCS)2] (1) and [(CuLR)2Cd(SCN)2] (2) have been synthesized using [CuL] and [CuLR] as ''metalloligands'' (where H2L = N,N'-bis(salicylidene)-1,4-butanediamine and H2LR = N,N'-bis(2-hydroxybenzyl)-1,4-butanediamine) respectively. Both the complexes were characterized by elemental analysis, various spectroscopic methods and single crystal XRD. Complex 1 is an angular trinuclear species, in which two terminal four-coordinate square planar ''metalloligands'' [CuL] are coordinated to a central Cd(II) through double phenoxido bridges along with two mutually cis nitrogen atoms of terminal thiocyanate ions. In complex 2, which is linear, in addition to the double phenoxido bridge, two SCN- coordinate to the trans positions of the central octahedral Cd(II) via S atoms. Theoretical calculations on the energetic difference between the two possible coordination modes of the thiocyanate anion to the Cd atom reveal that N-coordination is preferred over S-coordination in agreement with the much greater abundance of the reported N-bonded structures. In 2, there is a strong N-H . . . NCS-Cd H-bonding interaction, the binding energy of which is computed to be approximately -9.3 kcal mol-1, which is sufficient to compensate the 9.0 kcal mol-1 of energetic cost due to the unusual Cd-SCN coordination mode. [ABSTRACT FROM AUTHOR]

An oxime based tridentate Schiff base ligand 3-[3-(dimethylamino)propylimino]butan-2-one oxime (HL) produced two dinuclear compounds [Cu2L2(H2O)](ClO4)2 (1) and [Cu2L2(H2O)](BF4)2 (2), and a hexanuclear compound [{Cu3(HL)3(O3ClO)(μ3-O)}2(μ-H)](ClO4)7 (3) when it was reacted with Cu(ClO4)2·6H2O or Cu(BF4)2·6H2O at different pH values. All three compounds have been structurally and magnetically characterized. Compounds 1 and 2 are dinuclear species in which the two square planar copper(II) ions are joined solely by the double oximato bridges. On the other hand, the hexanuclear compound 3 consists of two triangular Cu3O cores held together by a proton separated by an O···O distance of 2.498(10) Å. The three square pyramidal copper(II) ions at the corners of an isosceles triangle form a triangular core through central oxido (μ3-O) and peripheral oximato bridges. Each triangular Cu3O core is capped by an unusual triply coordinated (μ3-perchlorato-O,O',O") perchlorate anion. Variable-temperature (2-300 K) magnetic susceptibility measurements show that compounds 1-3 exhibit a strong antiferromagnetic interaction with J values -562.6, -633.1 and -636.0 cm-1 respectively. The X-band EPR data at low temperature clearly indicate the presence of a spin frustration phenomenon in complex 3. [ABSTRACT FROM AUTHOR]

Three new hetero-metallic Cu(II)-Zn(II) compounds [(CuL1)2Zn(N(CN)2)2] (1), 2 ∞[(CuL2)2Zn(μ1-5-N(CN)2)2]n (2A) and 1 ∞[(CuL2)2Zn(μ1-5-N(CN)2)2]n (2B) have been synthesized by reacting a [CuL1] or [CuL2] "metalloligand" (where H2L1 = N,N'-bis(α-methylsalicylidene)-1,3-propanediamine and H2L1 = N,N'- bis(salicylidene)-1,3-propanediamine) with zinc perchlorate hexahydrate and sodium dicyanamide, using various molar ratios of the reactants. All three products have been characterized by IR and UV-Vis spectroscopies, ESI-MS, elemental, powder and single crystal X-ray diffraction analyses. Complex 1 is a discrete 0D trinuclear species in which two "metalloligands" coordinate to a zinc(II) ion through phenoxido oxygen atoms along with two terminal dicyanamido ligands. In contrast, products 2A and 2B are 2D and 3D coordination polymers, respectively, which bear a common [(CuL2)2Zn(N(CN)2)2] trinuclear unit wherein, however, dicyanamido moieties adopt a μ1-5-bridging coordination mode. The coordination networks have been formed via the linkage, in different manners, of the trinuclear nodes [(CuL2)2Zn]2+ through Zn and Cu centres with the help of divergent dicyanamido spacers. These two isomeric coordination polymers represent a rare example of "genuine supramolecular isomerism". The coordination networks in 2A and 2B have been classified from the topological viewpoint, revealing a binodal 3,4-connected underlying net with the 3,4L21 topology in 2A and a uninodal 4-connected underlying net with the qtz (quartz, 4/6/h1) topology in 2B. Electronic spectra and ESI mass spectra show that all three complexes lose their solid state identity in solution. [ABSTRACT FROM AUTHOR]

A new homometallic trinuclear Ni(II) complex [(NiL)2Ni(NCS)2] (1) and three heterometallic trinuclear Ni(II)-Zn(II)-Ni(II) complexes [(NiL)2Zn(NCS)2] (2), [(NiL)2Zn(NCS)2(CH3OH)2]·2CH3OH (3) and {[(NiL)2Zn(NCS)2(CH3OH)2]} {[(NiL)2Zn(NCS)2]} (4) have been synthesized by using the "complex as ligand" approach with the "metalloligand" [NiL] (H2L = N,N'-bis(salicylidene)-1,3-propanediamine) and thiocyanate in different ratios. All the complexes have been structurally and magnetically characterized. In the isomorphous complexes 1 and 2, the two terminal square planar Ni atoms and the central octahedral nickel atom (in 1) or zinc atom (in 2) are arranged in a bent structure where two cis ?N-SCN- thiocyanate ions are coordinated to the central atom. The chemical composition of 3 is very similar to that of 2 but, in 3, the central Zn atom is tetrahedral and the ?N-SCN- thiocyanate ions occupy an axial position of each terminal nickel atom (which now are octahedral with the sixth position occupied by a methanol molecule). Complex 4 consists of two closely related trinuclear units 4A and 4B. In 4A, the coordination environments of the metals are identical to those of 3 whereas 4B is a "coordination position isomer" of complex 2 with the central square pyramidal Zn and one of the terminal square pyramidal Ni atoms coordinated by two ?N-SCN- thiocyanate ions. Complex 4 is a unique example of a cocrystal formed by two similar trinuclear units (4A and 4B) where 4A is identical to an existing complex (3) and 4B is a "coordination position isomer" of another existing complex (2). [ABSTRACT FROM AUTHOR]

Four new hetero-metallic copper(ii)–cadmium(ii) complexes [{(CuL)2Cd}2(μ1,5-N(CN)2)2](ClO4)2·(H2O)2 (1), {[{(CuL)2Cd}2(μ1,3,5-N(CN)2)2](ClO4)2}n (2), {[(CuL)2Cd(μ1,5-N(CN)2)](ClO4)}n (3) and [(CuL)2Cd(μ1,5-N(CN)2)2]n (4) have been synthesized using a trinuclear hetero-metallic node, [(CuL)2Cd]2+ (where H2L = N,N′-bis(salicylidene)-1,3-propanediamine) and a dicyanamido spacer by varying the ratios of the reactants and temperature. The hetero-trinuclear node is formed in situ by the reaction of the “metalloligand” [CuL], cadmium perchlorate and sodium dicyanamide. All the complexes are structurally characterized. Complex 1 is a discrete hexanuclear cluster where two trinuclear nodes are connected through the Cd centres by convergent double μ1,5-dicyanamido spacers. Complex 2 is a 1D stair coordination polymer, in which the hexanuclear units are joined by the coordination of the central nitrogen atom of a μ1,3,5-dicyanamido ligand to the Cu atom of another unit. In contrast, complex 3 is a 1D zigzag chain, formed by connecting the Cd centre of trinuclear nodes via divergent μ−l,5-dicyanamido spacers. These three complexes contain a common [(CuL)2Cd(N(CN)2)]ClO4 trinuclear unit as the molecular building block. They represent an example of “supramolecular isomerism” of 0D/1D coordination polymers. On the other hand, replacement of the perchlorate ions from this trinuclear unit by another dicyanamido spacer results in complex 4, which is a 3D network, constructed by joining the trinuclear nodes through both Cd and Cu centers with the help of divergent dicyanamido spacers in the μ−l,5 mode. [ABSTRACT FROM AUTHOR]

Oxime-based tridentate Schiff base ligands 3-[2-(diethylamino)ethylimino]butan-2-one oxime (HL¹) and 3-[3-(dimethylamino)propylimino]butan-2-one oxime (HL²) produced the dinuclear complex [Ni2L¹2](ClO4)2 (1) and trinuclear complex [Ni3(HL²)3(µ3-O)](ClO4)4·CH3CN (2), respectively, upon reaction with Ni(ClO4)2·6H2O. However, in a slightly alkaline medium, both of the ligands underwent hydrolysis and resulted in tetranuclear complexes [{Ni(deen)(H2O)}2(µ3-OH)2{Ni2(moda)4}](ClO4)2·2CH3CN (3) and [{Ni(dmpn)(CH3CN)2}2(µ3-OH)2{Ni2(moda)4}](ClO4)2·CH3CN (4), where deen = 2-(diethylamino)ethylamine, dmpn = 3-(dimethylamino)-1-propylamine, and modaH = diacetyl monoxime. All four complexes have been structurally characterized. Complex 1 is a centrosymmetric dimer where the square planar nickel(II) atoms are joined solely by the oximato bridges. In complex 2, three square planar nickel atoms form a triangular core through a central oxido (µ3-O) and peripheral oximato bridges. Tetranuclear complexes 3 and 4 consist of four distorted octahedral nickel(II) ions held together in a rhombic chair arrangement by two central µ3-OH and four peripheral oximato bridges. Magnetic susceptibility measurements indicated that dinuclear 1 and trinuclear 2 exhibited diamagnetic behavior, while tetranuclear complexes 3 and 4 were found to have dominant antiferromagnetic intramolecular coupling with concomitant ferromagnetic interactions. Despite its singlet ground state, both 3 and 4 serve as useful examples of Kahn's model for competing spin interactions. High-frequency EPR studies were also attempted, but no signal was detected, likely due to the large energy gap between the ground and first excited state. Complexes 3 and 4 exhibited excellent catecholase-like activity in the aerial oxidation of 3,5-di-tert-butylcatechol to the corresponding o-quinone, whereas 1 and 2 did not show such catalytic activity. Kinetic data analyses of this oxidation reaction in acetonitrile revealed that the catalytic activity of 3 (kcat = 278.4 h-1) was slightly lower than that of 4 (kcat = 300.0 h-1). X-band EPR spectroscopy indicated that the reaction proceeded through the formation of iminoxyl-type radicals. [ABSTRACT FROM AUTHOR]

Abstract: Three new trinuclear hetero-metallic copper(II)–cadmium(II) complexes [(CuL)2Cd (NCS)2] (1A and 1B), [(CuL)2Cd(NCO)2] (2) have been synthesized using [CuL] as so-called “ligand complex” (where H2L= N,N′-bis(salicylidene)-1,3-propanediamine) and structurally characterized. Crystal structure analyses reveal that all three complexes have trinuclear entity in which two square planar [CuL] units are bonded to a cadmium ion through double phenoxido bridges. The Cd(II) is in a six-coordinate distorted octahedral environment being bonded additionally to two mutually cis nitrogen atoms of terminal thiocyanate (in 1A and 1B) and cyanate (in 2). Complexes 1A and 1B have the same molecular formula but crystallize in different monoclinic unit cells (P21/c for 1A and P21/n for 1B) and can be considered as polymorphs. On the other hand, complex 2 is crystallized only in one form and its conformation is similar to that observed in 1A. A theoretical investigation shows that 1A is slightly more (2.25kcal/mol) stable than 1B. However, in the crystal lattice, 1A establishes a C–H/π interaction while 1B interacts through a C–H···S hydrogen bond to form dimer and the more favorable dimerization energy in the later (ca. 3kcal/mol) compensates the difference in the relative energy of the polymorphs. Complex 2 crystallizes only in one form and conformation of the molecule is similar to 1A. Analyses of the noncovalent interactions of 2 show a weakening of the dimerization energy compared to 1A or 1B. Moreover, the H-bonding interaction that facilitates the formation of 1B is unlikely to be established in 2. Therefore this polymorph is not isolated. [Copyright &y& Elsevier]

Two new heterometallic copper(II)--mercury(II) complexes [(CuL)Hg(N3)2]n (1) and [(CuL)2Hg(N3)2] (2) and one copper(II)-cadmium(II) complex [(CuL)2Cd(N3)2] (3) have been synthesized using "metalloligand" [CuL] (where H2L = N,N'-bis(salicylidene)-l,3-propanediamine) and structurally characterized. Complex 1 is a one-dimensional (ID) helical coordination polymer constructed by the joining of the dinuclear [(CuL)Hg(N3)2] units through a single μ11 azido bridge. In the dinuclear unit the Hg(II) is bonded with two phenoxido oxygen atoms of "metalloligand" [CuL] and two nitrogen atoms of azido ligands. Complex 2 is a linear trinuclear entity, in which two terminal "metalloligands" [CuL] are coordinated to central Hg(II) through double phenoxido bridges. The azido ligands link the central mercury atom with the terminal copper atoms via μ1,3bridges. In contrast, the trinuclear complex 3 is bent. Here, in addition to two double phenoxido bridges, central Cd(II) is bonded to two mutually as nitrogen atoms of two terminal azido ligands. The variation in the coordination modes of the azido ligand seems to be responsible for the different molecular shapes of 2 and 3. Interestingly, bond distances between the Hg atoms and the central nitrogen atom of the azido ligands are 2.790(4) and 2.816(5) Á in 1 and 2.823(4) Á in 2. These bond distances are significantly less than the sum of van der Waals radii of mercury (2.04 Á) and nitrogen (1.55 Á) and considerably longer than the sum of their covalent radii (2.03 Â). However the distances are similar to reported Hg--N bond distances of some Hg(II) complexes. Therefore, we have performed a theoretical density functional theory study to know whether there is any interaction between the central nitrogen atom of the azido ligand and the mercury atoms. We have used the Bader's "atoms-in-molecules", energetic and orbital analyses to conclude that such interaction does not exist The probable reason for different molecular shapes observed in trinuclear complexes of 2 and 3 also has been studied and explained by theoretical calculations and using the CSD. Electronic spectra, EPR spectra and ESI mass spectra show that all three complexes lose their solid state identity in solution. [ABSTRACT FROM AUTHOR]

A diphenoxido-bridged dinuclear copper(ll) complex, [Cu2L2(ClO4)2 (1), has been synthesized using a tridentate reduced Schiff base ligand, 2-[[2-(diethylamino)-ethylamino]methyl]phenol (HL). The addition of triethyl-amine to the methanolic solution of this complex produced a novel triple bridged (double phenoxido and single hydroxido) dinuclear copper(ll) complex, [Cu2L2(OH)]ClO4 (2). Both complexes 1 and 2 were characterized by X-ray structural analyses, variable-temperature magnetic susceptibility measurements, and spectroscopic methods. In 1, the two phenoxido bridges are equatorial--equatorial and the species shows strong antiferromagnetic coupling with J = --6lS.6(6.l) cm-1. The inclusion of the equatorial--equatorial hydroxido bridge in 2 changes the CuṪCu distance from 3.018 Å (avg.) to 2.798 Å (avg.), the positions of the phenoxido bridges to axial--equatorial, and the magnetic coupling to ferromagnetic with J = 50.1(1.4) cm-1. Using 3,5-di-terf-butylcatechol as the substrate, the catecholase activity of the complexes has been studied in a methanol solution; compound 2 shows higher catecholase activity (kcat = 233.4 h-1) than compound 1 (kcat = 93.6 h-1). Both complexes generate identical species in solution, and they are interconvertible simply by changing the pH of their solutions. The higher catecholase activity of 2 seems to be due to the presence of the OH group, which increases the pH of its solution. [ABSTRACT FROM AUTHOR]

Three double phenoxido-bridged dinuclear nickel(II) complexes, namely [Ni2(L1)2(NCS)2] (1), [Ni2(L2)2(NCS)2] (2), and [Ni2(L3)2(NCS)2] (3) have been synthesized using the reduced tridentate Schiff-base ligands 2-[1-(3-methylamino-propylamino)-ethyl]-phenol (HL1), 2-[1-(2-dimethylamino-ethylamino)-ethyl]-phenol (HL2), and 2-[1-(3-dimethylamino-propylamino)-ethyl]-phenol (HL3), respectively. The coordination compounds have been characterized by X-ray structural analyses, magnetic-susceptibility measurements, and various spectroscopic methods. In all complexes, the nickel(II) ions are penta-coordinated in a square-pyramidal environment, which is severely distorted in the case of 1 (Addison parameter τ = 0.47) and 3 (τ = 0.29), while it is almost perfect for 2 (τ = 0.03). This arrangement leads to relatively strong antiferromagnetic interactions between the Ni(II) (S = 1) metal centers as mediated by double phenoxido bridges (with J values of -23.32 (1), -35.45 (2), and -34.02 (3) cm3 K mol-1, in the convention H = -2JS1S2). The catalytic activity of these Ni compounds has been investigated for the aerial oxidation of 3,5-di-tert-butylcatechol. Kinetic data analysis following Michaelis-Menten treatment reveals that the catecholase activity of the complexes is influenced by the flexibility of the ligand and also by the geometry around the metal ion. Electrospray ionization mass spectroscopy (ESI-MS) studies (in the positive mode) have been performed for all the coordination compounds in the presence of 3,5-DTBC to characterize potential complex-substrate intermediates. The mass-spectrometry data, corroborated by electron paramagnetic resonance (EPR) measurements, suggest that the metal centers are involved in the catecholase activity exhibited by the complexes. [ABSTRACT FROM AUTHOR]

Background: Viral infections are rising around the globe and with evolving virus types and increasing varieties of viral invasions; the human body is developing antimicrobial resistance continuously. This is making the fight of mankind against viruses weak and unsecured. On the other hand, changing lifestyle, globalization and human activities adversely affecting the environment are opening up risks for new viral predominance on human race. In this context the world has witnessed the pandemic of the human Coronavirus disease (COVID-19) recently. The disease is caused by the Coronavirus namely Severe Acute Respiratory Syndrome Coronavirus 2 (SARSCoV- 2)., Methods and Materials: Developing potential and effective vaccine is also time consuming and challenging. The huge resource of plants around us has rich source of potent antiviral compounds. Some of these molecules may serve as tremendously potent lead molecules whose slight structural modifications may give us highly bioactive antiviral derivatives of phytocompounds. Every geographical region is rich in unique plant biodiversity and hence every corner of the world with rich plant biodiversity can serve as abode for potential magical phytocompounds most of which have not been extensively explored for development of antiviral drug formulations against various viruses like the HIV, HPV etc. , and the Coronavirus, also known as SARS-CoV-2 which causes the disease COVID-19., Results: Several phytocompounds from various medicinal plants have already been screened using in silico tools and some of them have yielded promising results establishing themselves as potent lead molecules for development of drugs against the highly mutating SARS-CoV-2 virus and thus these phytocompounds may be beneficial in treating COVID-19 and help human to win the life threatening battle against the deadly virus., Conclusion: The best advantage is that these phytocompounds being derived from nature in most of the cases, come with minimum or no side effects compared to that of chemically synthesized conventional bioactive compounds and are indigenously available hence are the source of cost effective drug formulations with strong therapeutic potentials., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Correction for 'Mixed azido/phenoxido bridged trinuclear Cu(ii) complexes of Mannich bases: Synthesis, structures, magnetic properties and catalytic oxidase activities' by A. Ghosh et al., Dalton Trans., 2018, 47, 9385-9399.

Three similar Mannich base ligands viz. N,N-bis(3,5-dimethyl-2-hydroxybenzyl)-N',N'-dimethyl-1,3-diaminopropane (H2L1), N,N-bis(3,5-dimethyl-2-hydroxybenzyl)-N',N'-dimethyl-1,2-diaminoethane (H2L2) and N,N-bis(3,5-dimethyl-2-hydroxybenzyl)-N',N'-diethyl-1,2-diaminoethane (H2L3) upon reaction with Cu(CH3COO)2·H2O produced dinuclear complexes [Cu2L21-3]. The reaction of each of these isolated dimeric species with Cu(ClO4)2·6H2O and NaN3 resulted in three new trinuclear complexes, [(CuL1)2(μ1,1-N3)2Cu(H2O)]·CH3OH (1), [(CuL2)2(μ1,1-N3)2Cu(H2O)]·CH3OH (2) and [(CuL3)2(μ1,1-N3)2Cu(H2O)]·2CH3OH (3), respectively. The complexes (1-3) have been characterized by elemental analysis and single crystal X-ray diffraction. In all three complexes, the central Cu(ii) ion is coordinated by two terminal [CuL] units through a phenoxido and an azido bridge. These are the first trinuclear Cu(ii) complexes of this type of Mannich base ligands. Magnetic susceptibility measurements showed intramolecular antiferromagnetic interactions with J = -64.42, -9.60 and -4.54 cm-1 for 1, 2 and 3, respectively. All three complexes exhibited catecholase-like and phenoxazinone synthase-like activities towards the aerobic oxidation of 3,5-di-tert-butylcatechol and o-aminophenol, respectively. The turnover numbers (kcat) for the aerobic oxidation of 3,5-di-tert-butylcatechol are 568.8, 542.1 and 500.4 h-1 and those of o-aminophenol are 125.83, 118.9 and 114.7 h-1 for complexes 1-3, respectively. The X-band EPR spectroscopy and estimation of the produced hydrogen peroxide indicated that the aerobic oxidation of 3,5-di-tert-butylcatechol proceeded through the formation of a semiquinonate radical. The mechanism of phenoxazinone synthase-like activities is also proposed for trinuclear Cu(ii) catalysts with the help of mass spectral analysis.

Three new trinuclear hetero-metallic complexes [(CuL)2Zn(NCS)2] (1), [(CuL(R))2Zn(NCS)(μ1,1-NCS)] (2) and [(CuL(R))2Cd(μ1,3-NCS)2] (4) have been synthesized using [CuL] and [CuL(R)] as "metalloligands" (where H2L = N,N'-bis(salicylidene)-1,3-propanediamine and H2L(R) = N,N'-bis(2-hydroxybenzyl)-1,3-propanediamine). All three complexes are characterized by elemental analysis, spectroscopic methods and single crystal XRD. Complex 1 is an angular trinuclear species, in which two terminal four-coordinate square planar "metalloligands" [CuL] are coordinated to a central Zn(ii) through double phenoxido bridges along with two mutually cis nitrogen atoms of terminal isothiocyanate ions as is usually found in such complexes. In contrast, in complex 2, the two terminal "metalloligands" [CuL(R)] are square pyramidal, as one of the SCN(-) ions makes an unusual μ1,1-NCS bridge between copper centers while the other one coordinates to Zn(ii) through a N atom in a usual fashion making its geometry also square pyramidal. For 4 which possesses an angular trinuclear structure, in addition to double phenoxido bridges from two terminal [CuL(R)], both the SCN(-) ions are S-bonded to Cd(ii) and form a bridge (cis-μ1,3-SCN) between Cd(ii) and each of the terminal Cu(ii) ions. This structure is different from its unreduced analogue in which NCS(-) was N-terminal coordinated to Cd(ii) (3/3'). All the structures have been optimized using density functional theory (DFT) calculations. It has been found that for H2L, optimized structures like 1 and 2 differ only by 0.4 kcal mol(-1) but the H2L(R) structure 2 is more stable by 5.5 kcal mol(-1) than the structure resembling 1. For Cd(ii) complexes also, H2L optimized structures such as 3 and 4 do not differ significantly in energy (1.0 kcal mol(-1)) but the H2L(R) structure 4 is more stable than that of 3 by 4.6 kcal mol(-1). In fact, structure 4 has been found to be the most stable one among the other possible isomers of H2L(R).

Three new 2D coordination polymers (CPs) (2)∞[(NiL)2Ni(μ1,5-N(CN)2)2]n (), (2)∞[(NiL)2Cd(μ1,5-N(CN)2)2]n () and (2)∞[(NiL)2Zn(μ1,5-N(CN)2)2]n () have been synthesized by reacting a [NiL] "metalloligand" (where H2L = N,N'-bis(salicylidene)-1,3-propanediamine) with three different metal(ii) (Ni, Cd and Zn) perchlorates and sodium dicyanamide, with identical molar ratios of the reactants. All three products have been characterized by IR and UV-Vis spectroscopies, elemental analyses, powder and single crystal X-ray diffraction and variable temperature magnetic measurements. The isomorphous compounds and consist of similar [(NiL)2M(μ1,5-N(CN)2)] (M = Ni for and Cd for ) angular trinuclear units in which two terminal "metalloligands" [NiL] coordinate to the central nickel(ii) (in ) or cadmium(ii) (in ) ion through phenoxido oxygen atoms. The μ1,5-bridging dicyanamido spacers connect the central Ni(ii) or Cd(ii) of one node to terminal Ni(ii) of two different nodes giving rise to 2D CPs. Compound also contains trinuclear units with the same formula as those of and : [(NiL)2M(μ1,5-N(CN)2)] (M = Zn in ). The main differences are that these units are linear in and the dicyanamide spacers link only the nickel atoms of neighbouring nodes. As in and , these trinuclear units are connected to four other units via four μ1,5-bridging dicyanamido ligands, giving rise to 2D CP with a similar topology: a uninodal 4-connected underlying net with the sql (Shubnikov tetragonal plane net) topology and (4(4)·6(2)) point symbol. The magnetic properties show the presence of moderate intra-trimer antiferromagnetic interactions in (J = -12.9 cm(-1)) and weak antiferromagnetic interactions between the terminal Ni(ii) ions in (J = -2.4 cm(-1)). In the Ni(ii) ions are well isolated by the central Zn(ii) ion and accordingly, only a very weak antiferromagnetic interaction through the single μ1,5-bridging dicyanamido ligands is observed (J = -0.44 cm(-1), D = -3.9 cm(-1)).

A new homometallic trinuclear Ni(II) complex [(NiL)2Ni(NCS)2] (1) and three heterometallic trinuclear Ni(II)-Zn(II)-Ni(II) complexes [(NiL)2Zn(NCS)2] (2), [(NiL)2Zn(NCS)2(CH3OH)2]·2CH3OH (3) and {[(NiL)2Zn(NCS)2(CH3OH)2]} {[(NiL)2Zn(NCS)2]} (4) have been synthesized by using the "complex as ligand" approach with the "metalloligand" [NiL] (H2L = N,N'-bis(salicylidene)-1,3-propanediamine) and thiocyanate in different ratios. All the complexes have been structurally and magnetically characterized. In the isomorphous complexes 1 and 2, the two terminal square planar Ni atoms and the central octahedral nickel atom (in 1) or zinc atom (in 2) are arranged in a bent structure where two cis κN-SCN(-) thiocyanate ions are coordinated to the central atom. The chemical composition of 3 is very similar to that of 2 but, in 3, the central Zn atom is tetrahedral and the κN-SCN(-) thiocyanate ions occupy an axial position of each terminal nickel atom (which now are octahedral with the sixth position occupied by a methanol molecule). Complex 4 consists of two closely related trinuclear units 4A and 4B. In 4A, the coordination environments of the metals are identical to those of 3 whereas 4B is a "coordination position isomer" of complex 2 with the central square pyramidal Zn and one of the terminal square pyramidal Ni atoms coordinated by two κN-SCN(-) thiocyanate ions. Complex 4 is a unique example of a cocrystal formed by two similar trinuclear units (4A and 4B) where 4A is identical to an existing complex (3) and 4B is a "coordination position isomer" of another existing complex (2).

Two new heterometallic copper(II)-mercury(II) complexes [(CuL)Hg(N3)2]n (1) and [(CuL)2Hg(N3)2] (2) and one copper(II)-cadmium(II) complex [(CuL)2Cd(N3)2] (3) have been synthesized using "metalloligand" [CuL] (where H2L = N,N'-bis(salicylidene)-1,3-propanediamine) and structurally characterized. Complex 1 is a one-dimensional (1D) helical coordination polymer constructed by the joining of the dinuclear [(CuL)Hg(N3)2] units through a single μ-l,l azido bridge. In the dinuclear unit the Hg(II) is bonded with two phenoxido oxygen atoms of "metalloligand" [CuL] and two nitrogen atoms of azido ligands. Complex 2 is a linear trinuclear entity, in which two terminal "metalloligands" [CuL] are coordinated to central Hg(II) through double phenoxido bridges. The azido ligands link the central mercury atom with the terminal copper atoms via μ-l,3 bridges. In contrast, the trinuclear complex 3 is bent. Here, in addition to two double phenoxido bridges, central Cd(II) is bonded to two mutually cis nitrogen atoms of two terminal azido ligands. The variation in the coordination modes of the azido ligand seems to be responsible for the different molecular shapes of 2 and 3. Interestingly, bond distances between the Hg atoms and the central nitrogen atom of the azido ligands are 2.790(4) and 2.816(5) Å in 1 and 2.823(4) Å in 2. These bond distances are significantly less than the sum of van der Waals radii of mercury (2.04 Å) and nitrogen (1.55 Å) and considerably longer than the sum of their covalent radii (2.03 Å). However the distances are similar to reported Hg-N bond distances of some Hg(II) complexes. Therefore, we have performed a theoretical density functional theory study to know whether there is any interaction between the central nitrogen atom of the azido ligand and the mercury atoms. We have used the Bader's "atoms-in-molecules", energetic and orbital analyses to conclude that such interaction does not exist. The probable reason for different molecular shapes observed in trinuclear complexes of 2 and 3 also has been studied and explained by theoretical calculations and using the CSD. Electronic spectra, EPR spectra and ESI mass spectra show that all three complexes lose their solid state identity in solution.

Two new trinuclear hetero-metallic copper(II)-zinc(II) complexes [(CuL)(2)Zn(N(3))(2)] (1A and 1B) have been synthesized using [CuL] as a so-called "metalloligand" (where H(2)L = N,N'-bis(salicylidene)-1,3-propanediamine) and structurally characterized. Complexes 1A and 1B have the same molecular formula but crystallize in different crystal systems (triclinic for 1A and monoclinic for 1B) with space group P1 for 1A and P2(1)/c for 1B. 1A is an angular trinuclear species, in which two terminal four-coordinate square planar "metalloligand" [CuL] are coordinated to a central Zn(II) through double phenoxido bridges. The Zn(II) is in a six-coordinate distorted octahedral environment being bonded additionally to two mutually cis nitrogen atoms of terminal azide ions. In complex 1B, in addition to the double phenoxido bridge, the two terminal Cu(II) ions are linked to the central Zn(II) via a μ(-l,l) azido bridge giving rise to a square pyramidal environment around the Cu(II) ions and consequently the structure becomes linear. These two species can be considered as "linear-bent" isomers. EPR spectra and ESI mass spectra show that the two isomers are identical in solution. The DFT calculation reveals that the energy of 1A is 7.06 kcal mol(-1) higher than that of 1B. The existence of both isomers in the solid state suggests that crystal packing interactions in are more efficient and probably compensate for the difference in energy.