Nitrification and urease inhibitors mitigate global warming potential and ammonia volatilization from urea in rice-wheat system in India: A field to lab experiment.

The efficacy of alternative nitrogenous fertilizers for mitigating greenhouse gas and ammonia emissions from a rice-wheat cropping system in northern India was addressed in a laboratory incubation experiment using soil from a 10-year residue management field experiment (crop residue removal, CRR, vs. incorporation, CRI). Neem coated urea (NCU), standard urea (U), urea ammonium sulfate (UAS), and two alternative fertilizers, urea + urease inhibitor NBPT (UUI) and urea + urease inhibitor NBPT + nitrification inhibitor DMPSA (UUINI) were compared to non-fertilized controls for four weeks in incubation under anaerobic condition. Effects of fertilizers on global warming potential (GWP) and ammonia volatilization were dependent on residue treatment. Relative to standard urea, NCU reduced GWP by 11 % in CRI but not significantly in CRR; conversely, UAS reduced GWP by 12 % in CRR but not significantly in CRI. UUI and UUINI reduced GWP in both residue treatments and were more effective in CRI (21 % and 26 %) than CRR (15 % and 14 %). Relative to standard urea, NCU increased ammonia volatilization by 8 % in CRI but not significantly in CRR. Ammonia volatilization was reduced most strongly by UUI (40 % in CRI and 37 % in CRR); it was reduced 28-29 % by UUINI and 12-15 % by UAS. Overall, the urease inhibitor, alone and in combination with the nitrification inhibitor, was more effective in mitigating greenhouse gas and ammonia emissions than NCU. However, these products need to be tested in field settings to validate findings from the controlled laboratory experiment.

Enhancing cation and anion exchange capacity of rice straw biochar by chemical modification for increased plant nutrient retention.

Biochar, a potential alternative of infield crop residue burning, can prevent nutrient leaching from soil and augment soil fertility. However, pristine biochar contains low cation (CEC) and anion (AEC) exchange capacity. This study developed fourteen engineered biochar by treating a rice straw biochar (RBC-W) first separately with different CEC and AEC enhancing chemicals, and then with their combined treatments to increase CEC and AEC in the novel biochar composites. Following a screening experiment, promising engineered biochar, namely RBC-W treated with O3-HCl-FeCl3 (RBC-O-Cl), H2SO4-HNO3-HCl-FeCl3 (RBC-A-Cl), and NaOH-Fe(NO3)3(RBC-OH-Fe), underwent physicochemical characterization and soil leaching-cum nutrient retention studies. RBC-O-Cl, RBC-A-Cl, and RBC-OH-Fe recorded a spectacular rise in CEC and AEC over RBC-W. All the engineered biochar remarkably reduced the leaching of NH4+-N, NO3- -N, PO43--P and K+ from a sandy loam soil and increased retention of these nutrients. RBC-O-Cl at 4.46 g kg-1 dosage emerged as the most effective soil amendment increasing the retention of above ions by 33.7, 27.8, 15.0, and 5.74 % over a comparable dose of RBC-W. The engineered biochar could thus enhance plants' nutrient use efficiency and reduce the use of costly chemical fertilizers that are harmful to environmental quality.

Complimentary effect of exogenous enzymes, essential amino acids and essential fatty acids supplemented de-oiled rice bran (DORB) based diets on hematology, liver and intestinal histoarchitecture in Labeo rohita.

A 60-day feeding trial was conducted to study the hematology, liver, and intestinal histoarchitecture of Labeo rohita fed with a combination of exogenous enzymes, essential amino acids, and essential fatty acids to DORB (De-oiled rice bran) based diets. Three treatments viz., T1 [DORB + phytase and xylanase (0.01% each)], T2 [DORB + phytase (0.01%) + xylanase (0.01%) + L-lysine(1.4%) + L-methionine (0.4%) + EPA and DHA (0.5%)] and T3 [DORB + phytase (0.01%), xylanase and cellulase (0.075%) + L-lysine (1.4%) +L-methionine (0.4%) + EPA and DHA (0.5%)] were used in the present study. Serum total protein, albumin content and A/G ratio varied significantly (p < 0.05) among groups. Globulin content did not vary significantly among groups (p ≥ 0.05). The Hb content, RBC and MCV count varied significantly (p < 0.05) whereas MCH, MCHC content, WBC and lymphocyte count did not vary significantly among groups (p > 0.05). The liver and intestine examination revealed no visible alteration and showed normal histo-architecture. Based on the finding it is concluded that DORB supplemented with exogenous enzymes, essential amino acids and essential fatty acids with phytase (0.01%), xylanase and cellulase (0.075%), L-lysine (1.4%), DL-methionine (0.4%) and EPA and DHA (0.5%) improves the health of L. rohita.

Conventional and Zero Tillage with Residue Management in Rice-Wheat System in the Indo-Gangetic Plains: Impact on Thermal Sensitivity of Soil Organic Carbon Respiration and Enzyme Activity.

The impact of global warming on soil carbon (C) mineralization from bulk and aggregated soil in conservation agriculture (CA) is noteworthy to predict the future of C cycle. Therefore, sensitivity of soil C mineralization to temperature was studied from 18 years of a CA experiment under rice-wheat cropping system in the Indo-Gangetic Plains (IGP). The experiment comprised of three tillage systems: zero tillage (ZT), conventional tillage (CT), and strip tillage (ST), each with three levels of residue management: residue removal (NR), residue burning (RB), and residue retention (R). Cumulative carbon mineralization (Ct) in the 0-5 cm soil depth was significantly higher in CT with added residues (CT-R) and ZT with added residues (ZT-R) compared with the CT without residues (CT-NR). It resulted in higher CO2 evolution in CT-R and ZT-R. The plots, having crop residue in both CT and ZT system, had higher (p < 0.05) Van't-Hoff factor (Q10) and activation energy (Ea) than the residue burning. Notably, micro-aggregates had significantly higher Ea than bulk soil (~14%) and macro-aggregates (~40%). Aggregate-associated C content was higher in ZT compared with CT (p < 0.05). Conventional tillage with residue burning had a reduced glomalin content and ß-D-glucosidase activity than that of ZT-R. The ZT-R improved the aggregate-associated C that could sustain the soil biological diversity in the long-run possibly due to higher physical, chemical, and matrix-mediated protection of SOC. Thus, it is advisable to maintain the crop residues on the soil surface in ZT condition (~CA) to cut back on valuable C from soils under IGP and similar agro-ecologies.

Nitrogen-enriched biochar co-compost for the amelioration of degraded tropical soil.

Tropical soils are often deeply weathered and vulnerable to degradation having low pH and unfavorable Al/Fe levels, which can constrain crop production. This study aims to examine nitrogen-enriched novel biochar co-composts prepared from rice straw, maize stover, and gram residue in various mixing ratios of the biochar and their feedstock materials for the amelioration of acidic tropical soil. Three pristine biochar and six co-composts were prepared, characterized, and evaluated for improving the chemical and biological quality of the soil against a conventional lime treatment. The pH, cation exchange capacity (CEC), calcium carbonate equivalence (CCE) and nitrogen content of co-composts varied between 7.78-8.86, 25.3-30.5 cmol (p+) kg-1, 25.5-30.5%, and 0.81-1.05%, respectively. The co-compost prepared from gram residue biochar mixed with maize stover at a 1:7 dry-weight ratio showed the highest rise in soil pH and CEC, giving an identical performance with the lime treatment and significantly better effect (p < .05) than the unamended control. Agglomerates of calcite and dolomite in biochar co-composts, and surface functional groups contributed to pH neutralization and increased CEC of the amended soil. The co-composts also significantly (p < .05) increased the dehydrogenase (1.87 µg TPF g-1 soil h-1), ß-glucosidase (90 µg PNP g-1 soil h-1), and leucine amino peptidase (3.22 µmol MUC g-1 soil h-1) enzyme activities in the soil, thereby improving the soil's biological quality. The results of this study are encouraging for small-scale farmers in tropical developing countries to sustainably reutilize crop residues via biochar-based co-composting technology.

Physio-molecular traits of contrasting bread wheat genotypes associated with 15N influx exhibiting homeolog expression bias in nitrate transporter genes under different external nitrate concentrations.

MAIN CONCLUSION: The high affinity nitrate transport system is a potential target for improving nitrogen use efficiency of bread wheat growing either under optimal or limiting nitrate concentration. Nitrate uptake is one of the most important traits to take into account to improve nitrogen use efficiency in wheat (Triticum aestivum L.). In this study, we aimed to gain an insight into the regulation of NO3- -uptake and translocation systems in two contrasting wheat genotypes [K9107(K9) vs. Choti Lerma (CL)]. Different conditions, such as NO3--uptake rates, soil-types, N-free solid external media, and external NO3- levels at the seedling stage, were considered. We also studied the contribution of homeolog expression of five genes encoding two nitrate transporters in the root tissue, along with their overall transcript expression levels relative to specific external nitrate availability. We observed that K9107 had a higher 15N influx than Choti Lerma under both limiting as well as optimum external N conditions in vermiculite-perlite (i.e., N-free solid) medium, with the improved translocation efficiency in Choti Lerma. However, in different soil types, different levels of 15N-enrichment in both the genotypes were found. Our results also demonstrated that the partitioning of dry matter in root and shoot was different under these growing conditions. Moreover, K9107 showed significantly higher relative expression of TaNRT2.1 at the lowest and TaNPF6.1 and TaNPF6.2 at the highest external nitrate concentrations. We also observed genotype-specific and nitrate starvation-dependent homeolog expression bias in all five nitrate transporter genes. Our data suggest that K9107 had a higher NO3- influx capacity, involving different nitrate transporters, than Choti Lerma at the seedling stage.

Changes in weight gain, digestive and metabolic enzyme activities in Labeo rohita fingerlings in response to multiple stress exposure and dietary nutraceutical.

A feeding trial was conducted for 4 months to study the effect of a nutraceutical conglomerate at different levels (0, 0.1, and 0.5%) on stress-exposed (high stocking density, H and feed restriction, R) Labeo rohita fingerlings. Six isonitrogenous diets with a crude protein of 35% were prepared for the different treatments, viz. THR0, THR1, THR5, TNS0, TNS1 and TNS5. Stress significantly reduced the weight gain and feeding of 0.1% nutraceutical improved it in both stress-exposed and non-exposed groups from 3 months onwards. Two-and three-month stress-exposed groups exhibited lower (p < 0.05) protease activity, while amylase activity was significantly higher in 2-month stress-exposed groups. Higher lipase activity was found in stress-exposed groups irrespective of the duration of stress. Higher serum glutathione peroxidase (GPx), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and hepatic and muscle lactate dehydrogenase (LDH) activities were observed in the THR0 groups; however, THR1 showed a lower activity of these enzymes. Increased malate dehydrogenase (MDH) and glucose-6-phosphate dehydrogenase (G6PDH) activity was recorded in the 1st and 2nd months stress-exposed groups. However, THR1 group exhibited a reduced MDH and G6PDH activity compared to THR0 group in 1st and 2nd months. Hence, it can be concluded that the duration of multiple stress exposure adversely affected the digestive and metabolic enzymes activities and feeding of 0.1% nutraceutical conglomerates could restore the activities of digestive and metabolic enzymes in rohu fingerlings.

Plummeting anthropogenic environmental degradation by amending nutrient-N input method in saffron growing soils of north-west Himalayas.

Nitrous-oxide emission and nitrate addition from agriculture to earth's environment are two main agriculture related anthropogenic causes of environmental degradation that needs greater attention. For addressing the aforesaid issue, new techniques/practices need to be developed and implemented. The present investigation, which was focused on this issue, resulted in developing a new mode of nitrogen (N) placement, i.e. 'mid rib placement upper to corms in two splits (MRPU-2S)', that could reduce nitrous oxide N emission by around 70.11% and, nitrate N leaching and runoff by around 68.26 and 67.09%, respectively, over conventional method, in saffron growing soils of northwest Himalayas. Besides plummeting environmental degradation, MRPU-2S further resulted in enhancing saffron yield by 33.33% over conventional method. The findings of the present investigation were used to develop new empirical models for predicting saffron yield, nitrate N leaching and nitrous-oxide N emission. The threshold limits of nitrate N leaching and nitrous oxide N emission have also been reported exclusively in the present study.

Exogenous phytase and xylanase supplementation of formulated diets for rohu (Labeo rohita): impact on haematology, histology and IGF I gene expression.

The present study aims to delineate the effect of exogenous enzyme supplementation of fermented or non-fermented de-oiled rice bran (DORB) on haematology, histology and expression of IGF I gene expression of Labeo rohita. Four test diets, namely, T1 (DORB), T2 (fermented DORB), T3 (DORB+exogenous enzyme) and T4 (fermented DORB+exogenous enzyme) were formulated and fed to the L. rohita for a period of 60 days. The test diets T3 and T4 were supplemented with 0.1 g kg-1 xylanase (16,000 U kg-1) and 0.1 g kg-1 phytase (500 U kg-1) enzymes. A total of 120 juveniles of L. rohita (average weight 5.01 ± 0.02 g) were stocked in 12 rectangular tanks with 10 fish per tank in triplicates. At the end of the experiment, haematology, histology and IGF I gene expression of the different groups were analysed. The haemoglobin (Hb) content, RBC count and WBC count of L. rohita varied significantly (p < 0.05) among different groups. T3 diet-fed group had the highest Hb content, RBC count and WBC count as compared to the other groups. The MCV content was significantly (p < 0.05) lower in T3 group. The DORB type, exogenous enzyme supplementation and their interaction have no significant (p > 0.05) effect on MCH, MCHC and lymphocyte content of the cultured fish. The group which were fed T3 diet had significantly (p < 0.05) higher IGF-I gene expression as compared to other groups. The histological examination of liver revealed no pathological alteration of this organ. Similarly, there were no pathological changes observed in intestinal tissue in any dietary treatment group. Based on the findings of the present study, it is concluded that exogenous enzyme supplementation of DORB-based diets improves the physiological status and growth performances of Labeo rohita.

Evolution of pure hydrocarbon hosts: simpler structure, higher performance and universal application in RGB phosphorescent organic light-emitting diodes.

In the field of phosphorescent organic light-emitting diodes (PhOLEDs), designing high-efficiency universal host materials for red, green and blue (RGB) phosphors has been quite a challenge. To date, most of the high-efficiency universal hosts reported incorporate heteroatoms, which have a crucial role in the device performance. However, the introduction of different kinds of heterocycles increases the design complexity and cost of the target material and also creates potential instability in the device performance. In this work, we show that pure aromatic hydrocarbon hosts designed with the 9,9'-spirobifluorene scaffold are high-efficiency and versatile hosts for PhOLEDs. With external quantum efficiencies of 27.3%, 26.0% and 27.1% for RGB PhOLEDs respectively, this work not only reports the first examples of high-efficiency pure hydrocarbon materials used as hosts in RGB PhOLEDs but also the highest performance reported to date for a universal host (including heteroatom-based hosts). This work shows that the PHC design strategy is promising for the future development of the OLED industry as a high-performance and low-cost option.

Physio-metabolic and haematological changes of Labeo rohita fed with graded level of de-oiled rice bran-based diet.

A 60-day feeding trial was conducted with six experimental diets containing 260 g/kg crude protein and 70 g/kg lipid with varying level of de-oiled rice bran (DORB), viz., 33 (T33), 38 (T38), 43 (T43), 48 (T48), 53 (T53) and 58% (T58) to assess the digestive, metabolic and haematological responses in Labeo rohita. One hundred and eighty (180) fingerlings with ten fish per tank having an average weight of 9.8 ± 0.5 g were randomly distributed within six treatments in triplicates following a completely randomised design. The amylase and lipase activities in the whole intestine did not vary significantly (P > 0.05), but protease activity varied significantly with respect to DORB level in the diet. At higher (53 and 58%) inclusion level of DORB, the protease activities were lower. T33, T38 and T43 groups showed significantly (P < 0.05) higher aspartate aminotransferase (AST) activity compared to the other groups, whereas lowest activity was recorded in the group fed with highest inclusion level (58%). The oxidative stress enzyme like superoxide dismutase (SOD), catalase and glutathione-S-transferase exhibited significantly higher activities in liver of T58 group of L. rohita. However, the activity of catalase and SOD showed no significant variation in gill tissue. The haematological parameter values such as red blood cell (RBC), white blood cell (WBC), haemoglobin (Hb) and packed cell volume (PCV) were lower in the highest DORB fed group (T58) as compared to their lower DORB inclusion counterparts. No change in NBT value was recorded irrespective of DORB inclusion level in the diet. Hence, from these results, it can be concluded that the dietary inclusion of DORB up to 43% in the diet of L. rohita at 26% crude protein and 7% lipid level is best for the optimal activity of digestive, metabolic and haematological parameters.

Solid state fermentation of de-oiled rice bran: Effect on in vitro protein digestibility, fatty acid profile and anti-nutritional factors.

An experiment was conducted to study the effect of solid state fermentation of de-oiled rice bran (DORB) with Rhizopus oryzae on in vitro protein digestibility, anti-nutritional factors and fatty acid profile. The fermentation of DORB with Rhizopus oryzae significantly reduced the in vitro protein digestibility of DORB (p < .05). The fermentation of DORB with Rhizopus oryzae increased the saturated fatty acid (SFA) content by 46.83%, while decreased the MUFA and PUFA contents by 14.01 and 8.76%, respectively. The n-6 fatty acid content of FDORB increased by 6.19%, while n-3 fatty acid content decreased by 53.92%. The fermentation of DORB resulted in significant reduction in phytate and trypsin inhibitor activity (p < .05). Based on the present result it is concluded that the fermentation of DORB with Rhizopus oryzae improves the n-6 fatty acid profile and brings significant reduction in the phyate and trypsin inhibitor content but fails to improve the in vitro protein digestibility and hence cannot be recommended as a suitable microbe for DORB fermentation.

Comparative evaluation of fermented and non-fermented de-oiled rice bran with or without exogenous enzymes supplementation in the diet of Labeo rohita (Hamilton, 1822).

A 60-day feeding trial was conducted to study the effect of exogenous enzymes (xylanase and phytase) supplementation in the non-fermented and fermented de-oiled rice bran (DORB)-based diet of Labeo rohita. Four test diets (T1-DORB-based diet, T2-fermented DORB-based diet, T3-phytase and xylanase supplemented DORB-based diet, and T4-phytase and xylanase supplemented fermented DORB-based diet) were formulated and fed to the respective groups. Test diets T3 and T4 were supplemented with 0.01% xylanase (16,000 U kg-1) and 0.01% phytase (500 U kg-1) enzymes. One hundred twenty juveniles of L. rohita, with an average weight 5.01 ± 0.02 g, were stocked in 12 uniform size plastic rectangular tanks in triplicate with 10 fishes per tank following a completely randomized design (CRD). Exogenous enzyme supplementation to the T3 group significantly improved the growth performance of L. rohita (p < 0.05). Fermented DORB fed groups registered significantly lower growth irrespective of the supplementation of exogenous enzymes. The carcass composition (except CP %), enzyme activities (except amylase activity), globulin, and A/G ratio did not vary significantly (p > 0.05). Based on the results of the present study, it is concluded that exogenous enzyme supplementation significantly increases the growth of fish fed with DORB-based diet.

Design and Synthesis of Tris-Heteroleptic Cyclometalated Iridium(III) Complexes Consisting of Three Different Nonsymmetric Ligands Based on Ligand-Selective Electrophilic Reactions via Interligand HOMO Hopping Phenomena.

In this article we report on the successful synthesis and isolation of cyclometalated Ir complexes having three different nonsymmetric ligands based on ligand-selective electrophilic reactions via interligand HOMO (highest occupied molecular orbital) hopping phenomena. It was hypothesized that the electrophilic substitution reactions of bis-heteroleptic Ir complexes having 8-benzenesulfonamidoquinoline as an ancillary ligand, 5a and 7, would proceed at the 5 position of the quinoline ring of these Ir complexes to afford 18 and 19, because their HOMOs are localized on the quinoline rings, as predicted by density functional theory (DFT) calculations. In these products, the HOMO is transferred to one of two ppy ligands, in which the phenyl group is trans to the Ir-N (1 position of quinoline) bond, and hence, the iodination or formylation of 18 and 19 occurs at the 5' position of the ppy ligand to provide 20a, 23, and 24. Furthermore, we carried out the functionalization of 20a using cross-coupling reactions to obtain tris-heteroleptic Ir complexes containing three different ligands in good yields with negligible diastereomer formation. Photochemical properties, especially dual emission, and response to pH change, of new dual-emissive tris-heteroleptic cyclometalated Ir complexes, 21-24, are also reported.

Efficient Synthesis of Tris-Heteroleptic Iridium(III) Complexes Based on the Zn2+-Promoted Degradation of Tris-Cyclometalated Iridium(III) Complexes and Their Photophysical Properties.

We report on the efficient synthesis of tris-heteroleptic iridium (Ir) complexes based on the degradation of tris-cyclometalated Ir complexes (IrL3, L: cyclometalating ligand) in the presence of Brønsted and Lewis acids such as HCl (in 1,4-dioxane), AlCl3, TMSCl, and ZnX2 (X = Br or Cl), which affords the corresponding halogen-bridged Ir dimers (µ-complexes). Tris-cyclometalated Ir complexes containing electron-withdrawing groups such as fluorine, nitro, or CF3 moieties on the ligands were less reactive. This different reactivity was applied to the selective degradation of heteroleptic Ir complexes such as fac-Ir(tpy)2(F2ppy) (fac-12) (tpy: 2-(4'-tolyl)pyridine and F2ppy: 2-(4',6'-difluorophenyl)pyridine), mer-Ir(tpy)2(F2ppy) (mer-12), and mer-Ir(mpiq)2(F2ppy) (mer-15) (mpiq: 1-(4'-methylphenyl)isoquinoline). For example, the reaction of mer-12 with ZnBr2 gave the heteroleptic µ-complex [{Ir(tpy)(F2ppy)(µ-Br)}2] 27b as a major product, resulting from the selective elimination of the tpy ligand of mer-12, and treatment of 27b with acetylacetone (acacH) afforded the corresponding tris-heteroleptic Ir complex Ir(tpy)(F2ppy)(acac)18. In addition, another tris-heteroleptic Ir complex 35a having 8-benzenesulfonylamidoquinoline (8BSQ) ligand was synthesized. Mechanistic studies of this degradation reaction and the photochemical properties, especially a dual emission, of these newly synthesized tris-heteroleptic Ir complexes are also reported.

Design and Synthesis of Heteroleptic Cyclometalated Iridium(III) Complexes Containing Quinoline-Type Ligands that Exhibit Dual Phosphorescence.

The design and synthesis of some cyclometalated iridium(III) complexes containing quinoline-type ligands as ancillary ligands are reported. The emission spectra of Ir(III) complexes containing a quinolinolate (6, 8, 10) moiety exhibit a single emission peak at ca. 590 nm, resulting in a red colored emission. However, Ir(III) complexes containing 8-sulfonamidoquinoline ligands (11, 13-21) exhibit two different emission peaks (dual emission) at ca. 500 nm and ca. 600 nm upon excitation at 366 nm, resulting in a red-colored emission for 11 and a pale yellow-colored emission for 14-18 at 298 K. Especially, a white emission was observed for 19 at 298 and 77 K in dimethyl sulfoxide. The mechanistic studies based on time-dependent density functional theory calculations and time-resolved emission spectroscopy suggest that this dual emission originates from two independent emission states.

Crystal structure of {6,6'-dihy-droxy-2,2'-[imino-bis-(propane-1,3-diyl-nitrilo-methanylyl-idene)]diphenolato-κ(5) O (1),N,N',N'',O (1')}copper(II).

The title compound, [Cu(C20H23N3O4)], crystallizes in the space group Cc with two independent mol-ecules in the asymmetric unit. The Cu(II) atoms are each coordinated by the penta-dentate Schiff base ligand in a distorted trigonal bipyramidal N3O2 geometry. The equatorial plane is formed by the two phenolic O atoms and the amine N atom, while the axial positions are occupied by the two imine N atoms. In the crystal, the two independent mol-ecules are each connected into a column along the b axis through inter-molecular O-H⋯O hydrogen bonds. The two independent columns are further linked through an N-H⋯O hydrogen bond, forming a double-column structure.

Crystal structure of {2-[({2-[(2-amino-ethyl)amino]-ethyl}imino)-meth-yl]-6-hy-droxy-phenolato-κ(4) N,N',N'',O (1)}(nitrato-κO)copper(II) ethanol 0.25-solvate.

In the crystal structure of the title mononuclear Cu(II) complex, [Cu(C11H16N3O2)(NO3)]·0.25C2H5OH, the complex molecules are linked by N-H⋯O and O-H⋯O hydrogen bonds, forming a dimer with an approximate non-crystallographic twofold rotation axis of symmetry. In the monomeric unit, the Cu(2+) ion exhibits a distorted square-pyramidal configuration, whereby the anionic [HL](-) Schiff base ligand binds in a tetradentate fashion via the O and the three N atoms which all are approximately coplanar. The O atom of a nitrate anion occupies the fifth coordination site, causing the Cu(II) atom to move slightly out of the approximate basal plane toward the bound nitrate group. The structure exhibits disorder of the ethanol solvent mol-ecule.

Synthesis, crystal structure and magnetic studies of tetranuclear hydroxo and ligand bridged [Co4(µ3-OH)2(µ2-dea)2(L-L)4]4Cl·8H2O [L-L = 2,2'-bipyridine or 1,10-phenanthroline] complexes with mixed valence defect dicubane core.

X-ray crystallography of the title complexes indicates a discrete mixed valence (Co2(II)-Co2(III)) defect dicubane molecular unit where each cobalt nucleus attains a distorted octahedral geometry. The α-diimine (L-L) chelator coordinated to each cobalt ion stops further polymerization or nuclearization. The water molecules in the lattice play a crucial role in the formation of the supramolecular architectures. Magnetic data were analyzed using the effective spin-1/2 Hamiltonian approach and the parameters are, J = 115(6) K, ΔJ = -57.0(1.2) K, g(xy) = 3.001(25), and g(z) = 7.214(7) for 1 and J = 115(12) K, ΔJ = -58.5(2.5) K, g(xy) = 3.34(5), and g(z) = 6.599(12) for 2 suggesting that only the g matrices are prone to the change of α-diimine chelator.