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SUMMARY Due to the variability of raw ingredient inputs into meat and bone meal (MBM), the nutritional composition of each batch can vary. An evaluation was performed to determine if the performance and yield of broilers grown to 49 d of age would be impacted by dietary inclusion of MBM with a consistent or a variable nutritional quality. MBM inclusion rate was 10, 7.5, and 5% for the starter, grower, and finisher periods, respectively. Live production data as well as processing data were collected to determine the performance of the bird. The performance data were then used on an economic evaluation. Evaluation of live production determined that the variable CP levels of the MBM had a negative effect on the growth performance as well as processing. This lack in final weights of the birds from the variable CP levels of MBM allowed for a greater cost margin in the economic evaluation. Thus, MBM with a consistent CP level, allowed for greater growth as well as more usable product. In return, gross margins were higher for birds fed a consistent MBM.

SUMMARY Phosphorus runoff from the land application of poultry litter has become a concern in watersheds in the Ozark Plateau region, prompting local growers to use alternative litter management practices. One option is the export of excess poultry litter from producers in nutrient-surplus watersheds to users located in areas where nutrient loads are not problematic. In 2006, nearly 100,000 tons of broiler and turkey litter was exported by BMPs Inc., a nonprofit corporation providing litter management services. However, breeder hen litter and pullet litter are rarely exported because there are limited outlets for these lower nutrient value litters. Another poultry industry by-product is eggshell waste from egg-breaking operations, most of which is currently landfilled at a cost of $25/ton. Composting was examined as an alternative method to convert litter and eggshell wastes into a marketable soil amendment, making use of the beneficial soil nutrients available in both; 4 blends and 2 production systems were analyzed. Process results indicated that during composting, the observed temperatures of each of the 4 blends were different, but all followed a similar trend throughout the production cycle. Functional group inventory and diversity analysis indicated that all blends fell within optimal ranges of microbial species, except for the ratio of aerobic to anaerobic bacteria; only blend 4 was within the optimal value for this parameter. Diversity values for each blend fell within the moderate diversity range (3 < d < 6.5). Maturity analysis results indicated that no blends were mature at 11 wk (index

Although Vector Autoregressive models are commonly used to forecast prices, specification of these models remains an issue. Questions that arise include choice of variables and lag length. This article examines the use of Forecast Error Variance Decompositions to guide the econometrician's model specification. Forecasting performance of Variance Autoregressive models, generated from Forecast Error Variance Decompositions, is analyzed within wholesale chicken markets. Results show that the Forecast Error Variance Decomposition approach has the potential to provide superior model selections to traditional Granger Causality tests.

We have studied the high spin and low spin structural phases of the two-step spin transition compound [Fe(bpp) 2 ](NCS) 2 ·2H 2 O (bpp: 2,6-bis(pyrazol-3-yl)pyridine) of different sample history with X-ray synchrotron ( λ ∼ 0.32 A) powder diffraction at different temperatures as well as with usual X-ray ( λ ∼ 1.54 A) powder diffraction at room temperature by performing rapid repeated scans at regular intervals of time. A structural phase transition occurs only during the first step of the spin transition. Time dependent interconversions of the two crystallographic phases have been observed at room temperature for this material. The results indicate that a soft X-ray (Cu-K α )-induced structural change occurs in this material at room temperature. Possible mechanisms for this unusual observation are discussed.

The U.S. poultry industry has spent considerable resources to date preparing for an outbreak of avian influenza in this country. This research quantifies the potential effects of two alternative avian influenza scenarios on the poultry industry. In addition, this research looks at effects on other agriculture sectors including the loss of feed demand from an outbreak and the impacts on aggregate measures like farm income and consumer food expenditures. The economic sector model maintained by the Food and Agricultural Policy Research Institute (FAPRI) is employed for these scenarios.

SUMMARY The poultry industry is an essential part of the region’s economy in western Arkansas and eastern Oklahoma. With poultry production has come large amounts of poultry litter to the region. Some suggest excess nutrients from poultry litter have negatively affected water, lowering its usefulness for recreational purposes. This conflict has put the poultry industry at the heart of environmental litigation in the region. The purpose of this paper was to examine, first, the economic contributions of the poultry industry in the region and, second, the potential economic costs associated with meeting water quality standards by reducing the amount of poultry litter produced. Results show that the poultry industry as a whole supports over 34,000 jobs in the northern economic region of the study area and nearly 15,500 jobs in the central region. Results also indicate that the economic activity in the northern region could decrease by around 2% and by over 3% in the central region due to regulations on the use of poultry litter. These results are useful for those interested in the economic contribution of the poultry industry to the region, including poultry integrators and producers as well as to policymakers looking to balance environmental quality and economic development.

We have studied the X-ray powder diffraction of the spin transition material [Fe(bpp)2](NCS)2 · 2H2O (bpp: 2,6-bis(pyrazol-3-yl)pyridine) at room temperature. Two crystallographic phases have been observed depending on the sample history of this material. The results obtained corroborate the earlier observations from magnetic and calorimetric studies. Relatively prolonged exposure of the sample to X-rays caused a structural change. LIESST and Reverse-LIESST effects, characterised by 57Fe Mossbauer spectroscopy, have been observed in this material.

The Illinois River Basin in eastern Oklahoma and northwest Arkansas is an example of a region where significant growth in poultry production has been accompanied by water quality problems. The primary concern in the basin is the problem of phosphorus in runoff that is associated with application of litter to crops. Existing data suggest that there has been a continuing decline in the quality of water in the Illinois River, and discussions have focused on developing and implementing a phosphorus standard. The specific objectives of this study are to estimate the reduction in poultry production necessary to achieve the reduction in phosphorus runoff under a set of phosphorus constraints, including soil test phosphorus, and to estimate the opportunity costs of reducing poultry production in the basin under each phosphorus constraint on the economic activity in the watershed. A mathematical programming model that incorporates poultry production and cropping decisions is developed. The parameters for ...

SUMMARY Nearly all broilers produced in the United States are grown under contract arrangement between independently contracting broiler producers and integrated poultry companies. These contracts may vary in some minor points, but all include general provisions stipulating that the integrators are responsible for chick placement, feed provision, and live hauling of slaughter weight broilers (weights and age to be determined by the integrators) with growers providing the housing and equipment (as specified by the integrators), labor, utilities, and management expertise, with periodic consultation by the integrator service personnel. From time to time, it is desirable to look at this production system and compare current structure, costs, and returns with those from past years. The Poultry Federation (comprised of poultry firms in Arkansas, Missouri, and Oklahoma) Board of Directors commissioned a study in June 1999 to be conducted later that year to quantify changes that occurred in the structure, costs, and returns in the region’s broiler industry during the period 1979 to 1999. Persons considering either entering the broiler business or seeking to expand existing operations can use these results. Lending institutions can use results in evaluation of loan applications for enterprise establishment or expansion. Broiler producers and integrated poultry companies can also use these results to compare costs and returns with past years and evaluate both the future state of the existing industry and opportunities for expansion.

The crystal structures of tris(2-methyl-1,10-phenanthroline)ruthenium(II) iodide, tris(6-methyl-2,2′-bipyridine)ruthenium(II) tetrafluoroborate and tris(6,6′-dimethyl-2,2′-bipyridine)ruthenium(II) tetrafluoroborate 0.75 hydrate are described. The average Ru–N distances in the complex cations are 2.063, 2.089, and 2.119 A, severally. The substituents in the ligands exert a strong influence on the geometry of the coordination core, which deviates significantly from regular octahedral. The deviation is most marked for the dimethyl-substituted system where pronounced inter-ligand forces result in gross angular distortion of the relative orientations of the three ligand molecules.

This study examines food consumption patterns for households in Siberian Russia. The study is based on a survey conducted by the American Business Center in Vladivostok in February/March 1996. When incomes grow, households tend to include greater proportions of livestock products in their diets. That leads to a corresponding increase in indirect cereal consumption. Alternative measures of food consumption employed in the analysis are expenditures and calories. The results show that the expenditure income elasticity of cereal products is positive whereas income elasticities of cereal products are zero for calorie measures, implying demand for service from non-agricultural sectors. The elasticities of total food and animal product consumption are positive for both measures. Stabilization of transition economies might lead to a substantial increase in indirect cereal consumption, which, in turn, would lead to a dramatic increase in demand for agricultural imports. [EconLit citations: L660, D120, Q180.] © 2004 Wiley Periodicals, Inc. Agribusiness 20: 129–141, 2004.

Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) thiocyanate dihydrate undergoes a two-step singlet (1A1) ⇄ quintet (5T2) transition in which both steps are associated with thermal hysteresis. Thermal cycling of the sample results in its conversion to a second phase which displays a single-step transition with a very narrow hysteresis loop. This second phase slowly reverts to the initial phase on standing at 300 K. The interconversions are completely reversible. The spin state changes have been monitored by measurement of magnetism and Mossbauer spectra and by differential scanning calorimetry (DSC) studies.

Interaction of 2,2′-bipyridine-6-carbothioamide (bta) with iron(II) chloride leads to three different products: [Fe(bta)2]Cl2·H2O, [Fe(bta)2][FeCl4] and an apparently ‘mono’-ligand complex analogous to the previously described Fe(pta)Cl2·H2O (pta = 1,10-phenanthroline-2-carbothioamide). Electronic and Mössbauer spectroscopic data show that all three complexes of bta contain the [Fe(bta)2]2+ cation. The Mössbauer spectra, together with the magnetic properties, indicate that the [Cl3Fe–O–FeCl3]2– ion is associated with the cation in the ‘mono’ complex which is formulated as [Fe(bta)2]2[Cl3Fe–O–FeCl3]Cl2·3H2O. The unusual temperature dependence of the Mössbauer spectrum, and the magnetism of this complex, arises from the presence of different iron sites, one being low-spin iron(II) and the other high-spin iron(III). Two of the latter are antiferromagnetically coupled in the oxobridged anion. 2,2′-Bipyridine-6-carboxamide (bca) yields an iron(II) mono-ligand derivative, Fe(bca)Cl2·H2O, which is a simple high-spin paramagnet.

The compound [Fe(phy)2](BF4)2 (phy = 1,10-phenanthroline-2-carbaldehyde phenylhydrazone) shows spin-transition with a hysteresis of 10 K width around room temperature. Continuous irradiation of the compound during heating and cooling with green light (514 nm) shifts the hysteresis in temperature.

The behaviour of spin crossover compounds is among the most striking and fascinating shown by relatively simple molecular species. This review aims to draw attention to the various ways in which spin crossover phenomena are manifested in iron(II) complexes, to offer some rationalisation for these, and to highlight their possible applications. Typical examples have been selected along with more recent ones in order to give an overall view of the scope and development of the area. The article is structured to provide the basic material for those who wish to enter the field of spin crossover.

The effect of hydrostatic pressure on the transition temperature and the hysteresis widths of first order spin crossover phase transitions has been studied. A decrease as well as an increase of the hysteresis width with increasing pressure was reported in the literature. The increase of width with increasing pressure contradicts the expectation derived from mean field theory. We remeasured the pressure dependence of the temperature hysteresis of the compound [Fe(phy)2](BF4)2 (phy=1, 10-phenanthroline-2-carbaldehydephenylhydrazone). The spin transition temperatures at ambient temperature are T ↑ 1/2 =289±1 K, T ↓ 1/2 =283±1 K . An increase of the hysteresis width of d Δ T 1/2 / d p=0.29 K kbar −1 up to p=4.1 kbar has been measured confirming the reported anomaly. The change of the average temperatures T1/2=1/2(T↑1/2+T↓1/2) at which the high spin fraction γ is 1/2 is determined to be 3.0±0.2 K kbar−1. Allowing for a pressure dependence of the bulk modulus of the compound, the anomalous increase of hysteresis width can be interpreted.

Replacement of one of the terminal pyridine rings in terpyridine by a thiozole ring has been found to have little effect on the field strength and the resultant 6-(thiazol-2-yl)-2,2′-bipyridine (thzbpy) yields a purely low-spin [Fe(II)N6]2+ derivative. When a methyl group is incorporated into the 4-position of the thiazolyl group (mthzbpy) the field strength is reduced but the [Fe(II)N6]2+ derivative remains low-spin at room temperature though there is evidence for the onset of a transition to high-spin species at elevated temperature. When the central ring of terpyridine is replaced by a thiazole to give 2,4-bis(pyridin-2-yl)thiazole (pythiaz) the effect is more pronounced and salts of the [Fe(II)N6]2+ derivative are high-spin at room temperature. The structures of [Fe(thzbpy)2][PF6]2, [Fe(mthzbpy)2][PF6]2 and [Fe(pythiaz)2][BF4]2 were determined. The FeN distances in the first two complexes are normal for low-spin iron(II), while in the last complex they are indicative of high-spin iron(II). Moreover, the distortion about the metal atom is high in the last complex. The results highlight the significance of the bonding to the central donor atom in determining the electronic properties of the complexes of these tridentate systems. [Fe(thzbpy)2][PF6]2 and [Fe(mthzbpy)2][PF6]2 are monoclinic, space group C2/c, with unit cell dimensions: a = 16.530(5), b = 22.356(4), c = 17.103(4) A , β = 90.99(1)°, Z = 8, for the former and a = 16.61(1), b = 22.80(1), c = 17.29(2) A , β = 90.66(4)°, Z = 8 , for the latter complex, [Fe(pythiaz)2][BF4]2 is tetragonal, space group P 4 2 1 c , with unit cell dimensions: a = b = 8.746 (2), c = 19.221(6) A , Z = 2 .

The iron(II) complex [Fe(bpp)2]-(CF3SO3)2 H2O (bpp = 2,6-bis(pyrazolyl-3-yl)pyridine) shows a thermal spin transition associated with a hysteresis of approximately 140 K width. The transition temperatures T1/2 (where the fraction of HS species γHS = 0.5) are 147 K and ≈285 K in the cooling and heating directions, respectively. The compound shows the LIESST and reverse-LIESST effects at low temperatures. The relaxation of the metastable HS states generated by LIESST was observed quantitatively at temperatures between 77.5 and 85 K by Mossbauer spectroscopy. Metastable HS states can also be generated by rapid cooling of the sample. The relaxation of the metastable HS states formed by thermal spin-state trapping was monitored at temperatures between 104 and 118 K by magnetic susceptibility measurements. The relaxation mechanisms of the HS states generated by LIESST and thermal spinstate trapping are completely different. We suggest that the HS → LS relaxation after thermal spin-state trapping is triggered by an additional structural phase transition of the system.

The purpose of this article is to explore the CWA’s regulatory impact on Arkansas’s agricultural producers. This article will discuss in the subsections below: 1) the jurisdiction and waters covered by the CWA; 2) the broad definition that has been given to the term “pollutant” by the courts and how some agricultural activities qualify as a “pollutant”; 3) point source and non-point sources of agricultural pollution; 4) the two types of CWA permits, National Pollution Discharge System (NPDES) permits and Section 404 permits that may be relevant for agricultural producers; and 5) the statutory requirement that certain animal feeding operations are required in certain situations to apply for a NPDES permit. The regulatory requirements on these animal feeding operation operators will be discussed to give these operators a better understanding the duties placed on them under the CWA.

Ultrafast transient absorption spectroscopy serves to identify the (3)dd state as intermediate quencher state of the (3)MLCT luminescence in the non-luminescent ruthenium complexes [Ru(m-bpy)3](2+) (m-bpy = 6-methyl-2,2'-bipyridine) and [Ru(tm-bpy)3](2+) (tm-bpy = 4,4',6,6'-tetramethyl-2',2'-bipyridine). For [Ru(m-bpy)3](2+), the population of the (3)dd state from the (3)MLCT state occurs within 1.6 ps, while the return to the ground state takes 450 ps. For [Ru(tm-bpy)3](2+), the corresponding values are 0.16 and 7.5 ps, respectively. According to DFT calculations, methyl groups added in the 6 and 6' positions of bipyridine stabilize the (3)dd state by ~4000 cm(-1) each, compared to [Ru(bpy)3](2+).

The di-imine system 3,3′-bipyridazine (L) generates a particularly strong ligand field and this is revealed in the low-spin nature of [FeL2(NCS)2] and of salts of [FeL3]2+, the appearance of a doublet ⇄ quartet transition in [CoL3]2+, and the high energy (13 200 cm−1) of the 3A2g → 3T2g transition in the electronic spectrum of [NiL3]2+. In attempts to prepare bis(ligand) complexes the mixed low-spin cationic, high-spin anionic complexes [FeL3][FeCl4], [FeL3][Fe(NCS)4] and [FeL3][FeCl4O]2 were isolated. These were characterised by magnetic and Mossbauer spectral measurements. The structures of both [FeL3][ClO4]2 and [NiL3][ClO4]2 reveal unusually short FeN (1.927(3) A) and NiN (2.060 A) distances and these, and the high field strength, are believed to result in part from the absence of ortho-hydrogen atoms in the ligand molecules which cause considerable inter-ligand repulsion in complexes of the related di-imine, 2,2′-bipyridine. [FeL3][ClO4]2 crystallises in space group P 3 c1 (Z=2) with cell parameters a=10.281(2), b=10.281(2), c=15.863(4) A. A total of 430 reflections with Io>3σ(Io) was observed and a final value of R=0.045 was obtained. [NiL3][ClO4]2 crystallises in space group P321 (Z=1) with cell parameters a=10.225(3), b=10.225(3), c=8.049(3) A. Stacking faults and twinning create an apparent P 6 2c diffraction symmetry. A total of 266 reflections with Io>3σ(Io) was observed and a final value of R=0.042 was obtained.

Tris(ligand)iron(II) complexes of 6-methyl-2,2′- bipyridine (mbpy) and 2-(pyridin-2-yl)quinoline (pyq) display anomalous magnetic properties which are associated with a temperature-induced singlet (1A1) ⇋ quintet (5T2) transition. Two forms of [Fe(pyq)3][ClO4]2 were obtained: one which is essentially high spin over the range 89–300 K and the other which shows an almost complete, gradual transition in this range. In the three complex salts of [Fe(mbpy)3]2+ isolated, the perchlorate, fluoroborate and hexafluorophosphate, appreciable spin- pairing is observed at low temperatures but in no instance is the transition to singlet state species complete at 89 K. Data for solutions of both [Fe (mbpy)3] [ClO4]2 and [Fe(pyq)3] [BF4]2 indicate that negligible spin-pairing is observed down to 210 K. Mossbauer spectral data confirm the change in spin state populations in all solid salts and moreover indicate two sites for the high-spin species at low temperatures. It is believed that these may arise from ordering of anion sites in the lattice. In the room temperature structure of [Fe(mbpy)3] [ClO4]2· 1 2 mbpy disorder of one of the anions as well as the occluded free ligand occurs. In the structure of the complex cation considerable distortion is observed with the average FeN distance being 2.21 A. The ligand molecules are not planar, the pyridyl rings being twisted 4.3, 16.4 and 17.8° about the inter- ligand bridge. The methyl substituent induces a steric barrier to coordination and also greater inter-ligand repulsions than in complexes of bpy and this is presumably responsible for the accessibility of the quintet state for Fe(II). The steric effects of the fused benzene ring in pyq are predicted to be similar. [Fe(mbpy)3] [ClO4]2· 1 2 mbpy crystallises in space group P21/c (Z = 4) with cell parameters a = 19.769(10), b = 13.186(4), c = 15.043(8) A. A total of 2509 reflections with Io > 3σ(Io) were observed and gave a final R = 0.057.

[Fe(bpp)2][Pt(ox)2].H2O (with bpp=2,6-bis(pyrazol-3-yl)-pyridine and ox=oxalate) was prepared, and its spin crossover behavior was characterized. The two-step spin transition behavior changes over several cycles. The original behavior is restored when the sample is allowed to relax for a week. Furthermore, the ST exhibits a strong dependence on the heating and cooling rate. Heating the compound at 1 K/min leads to a spin transition with a third step and a second plateau at gammaHS approximately 0.8. Quenching the sample to 77 K also affects the spin transition behavior. The kinetic relaxation is followed after quenching and after light-induced excited spin state trapping experiments.

Cobalt(II), a d 7 ion, can exist in a low spin doublet state or a high spin quartet state. Both spin-state configurations are known in four-, five- and six-coordinate complexes. For each of these coordination numbers, systems are known where the two spin states may be thermally interconverted. For four-coordinate and some five-coordinate systems these interconversions are best regarded as configurational equilibria; in other instances a spin transition is involved. The features of these transitions show similarities to, but also marked differences from, those in iron(II) systems. The smaller change in spin associated with the transition (ΔS=1) and the operation of a Jahn-Teller effect in the doublet state species confer special characteristics on the cobalt(II) systems.

Predominance of production and marketing contracts in the broiler industry suggests a traditional analysis of price relationships might no longer be appropriate. In this study, markets for broiler cuts are defined as spatial. Results of a vector autoregressive regression analysis of monthly USDA data from 1987 to 2000 verify the price relationship between white meat and whole broiler prices. Price shocks in the boneless skinless breast market have a greater effect than dark meat shocks, suggesting this market is most important in price transmission. These results will assist industry participants to form more effective marketing and pricing strategies, thus adding efficiency to the market.

This study presents a unique view on the USDA Food Safety and Inspection Service (USDA FSIS) implementation of the so-called “Mega-Reg” authorizing establishment of regulatory hazard analysis and critical control point (HACCP) procedures. Surveys were sent to plant managers of the 11 firms participating in the HACCP Roundtable at the University of Arkansas. Results of the survey were used to create HACCP implementation cost estimates for poultry kill plants and perform welfare analysis by using equilibrium displacement model (EDM). Results show average welfare losses up to 35 million a year for the broiler industry as well as substantial losses to consumers resulting from the new regulation.

International audience; The magnetic properties of aseries of hydrated and dehydrated spin crossover compounds derived from the 2,6-bis(pyrazol-3-yl)pyridine (bpp) ligand have been reinvestigated and the light-induced crossover studied at 10 K. The capacity of a compound to retain the light-induced HS information has been estimated through the determination of the T(LIESST). The position of each compound in the T(LIESST)-T1/2 diagram has been analyzed and the effect of the nature of the salt, hydration degree and cooperativity have been discussed.

Product placement survey data for 192 Asian-American households in Houston were used to analyze the value of rice quality attributes via the Consumer Goods Characteristics Model (CGCM). Five rice varieties were used for this study: domestic Lemont, Jasmine 85, Toro II, and two different Thai import varieties. For each variety, marginal implicit prices were calculated at the means for seven characteristics: color, texture, aroma, stickiness, flavor, aftertaste, and moisture.

Iron(II) has the 3d6 outer electronic configuration and hence its octahedral complexes may be either high-spin or low-spin. The high-spin configuration, t 2g 4 e g 2 , is adopted when relatively weak-field ligands are coordinated while the low-spin, t 2g 6 e g 0 , is obtained when strong-field ligands are involved. In Oh symmetry the ground states are 5T2g and lA1g, for the high-spin and low-spin configurations, respectively. While in most iron(II) six-coordinate complexes the symmetry is lower than Oh, these designations are generally adopted in the following sections for convenience. [Fe(H2O)6]2+ and [Fe(en)3]2+ (en = ethylenediamine) are typical examples of high-spin complexes, while [Fe(CN)6]4− and [Fe(bpy)3]2+ (bpy = 2,2′-bipyridine) contain strong-field ligands and are low-spin. The two configurations, represented in Fig. 1, differ in the number of unpaired electrons and hence they give rise to marked differences in all those properties of complexes which depend on electronic configuration. Important among these are magnetic and electronic spectral properties. In addition, the Mossbauer spectra for the two spin states are quite distinct and the spectral parameters are clearly diagnostic of the spin state, as is discussed in section 3.4. Further, the absence of electrons in the antibonding eg orbitals in the low-spin configuration allows closer approach of the donor atoms and hence stronger metal — donor atom interaction.

A letter written by Francis Lions to Linus Pauling in 1939 sheds light on the early development of Lions' work in the field of coordination chemistry. Together with the subject matter of some of his relatively early publications, it reveals how he was developing the synthetic strategies that later were applied to the successful design and function of sexadentate chelating agents.

Studies of the spin transition behavior of the mononuclear compound [Fe(pythiaz)2](BF4)2 have been carried out under hydrostatic pressures up to 9.13 kbar in the 5–300 K temperature range. Under ambient pressure this compound exhibits an approximately half-step (incomplete) HS ↔ LS transition with T1/2 = 146 K without any thermal hysteresis. At pressures up to 4.5 kbar the behavior remains similar but with an upward displacement of T1/2 and a slight decrease in the residual high spin fraction at low T . Application of higher pressures resulted in an almost complete two-step spin transition with several unusual pressure effects. Along with the expected pressure dependence of T1/2 the surprising appearance of hysteresis in the spin transition curves was observed. It is suggested that the likely origin of this unprecedented behavior is a pressure-induced structural change.

The structures of a series of hydrated complex chlorides [Fe(btp)2]Cl2·6H2O, [M(bpp)2]Cl2·6.5H2O (M = Fe, Ru) and [Ru(terpy)2]Cl2·6H2O are described (btp = 2,6-bis(1,2,4-triazol-3-yl)pyridine; bpp = 2,6-bis(pyrazol-3-yl)pyridine; terpy = 2,2′∶6′,2″-terpyridine). The ligands are all of the terimine type. [Fe(btp)2]Cl2·6H2O is high spin while [Fe(bpp)2]Cl2·6.5H2O is low spin, the difference in the average Fe–N distance in the two complexes being 0.24 A. In all four complex salts there is extensive hydrogen bonding between the water and chloride ions. In addition, for the pyrazolyl and triazolyl ligands this involves the uncoordinated >NH groups. The arrangement of the cations in the four lattices is discussed in terms of the previously described “terpy embrace” adopted widely by bis(terimine)metal systems.

Comparison of the Mossbauer spectral data for low-spin tris(ligand) iron(II) complexes of the series of bidentate N–N ligands 2,2′-bipyridine (bpy), 4-(pyridin-2-yl)thiazole (4pyt), 2-(pyridin-2-yl)thiazole (2pyt), 4,4′-bithiazole (4bt) and 2,2′-bithiazole (2bt) shows a progressive reduction in the p-acceptor character of the ligand with increase in the number of thiazole rings, the effect being greater for the 4-thiazolyl derivatives. The structure of [Fe(4pyt)3]2+ is remarkably similar to that of [Fe(bpy)3]2+ with an average Fe–N distance of 1.96 A. Attempts to characterize structurally [Fe(2bt)3]2+ were not successful and led to crystallization of [Fe(2bt)2(H2O)2] [ClO4]2·(2bt)4. In the complex cation, which has the trans structure, the average Fe–N distance is 2.21 A and the Fe–O distance is 2.08 A. Mossbauer spectral data indicate a quintet ground state for this species. [Fe(4pyt)3] [BF4]2·H2O: monoclinic, space group P21/c, a 10.213(7), b 13.436(6), c 23.12(1) A, b 109.65(3)˚, Z 4. [Fe(2bt)2(H2O)2] [ClO4]2·(2bt)4: triclinic, space group P–1, a 10.822(7), b 11.451(8), c 12.945(8) A, a 70.31(5), b 69.92(5), g 63.32(6)˚, Z 1.

Essentially high-spin [Fe(bpp)2][NCS]2·2H2O and [Fe(bpp)2][NCSe]2 (bpp = 2,6-bis(pyrazol-3-yl)pyridine) were isolated from an aqueous reaction mixture. Both salts undergo an abrupt transition to low spin below room temperature, that for the thiocyanate occurring in two steps and the high-spin Æ low-spin Æ high-spin cycle being accompanied by hysteresis in both steps. Recrystallization of the salts from nitromethane yielded a mixture from which bright yellow crystals were separated for structure determination. In addition, from the recrystallized selenocyanate, deep red-brown crystals of composition [Fe(bpp)2][NCSe]2·H2O·0.25 CH3NO2 were obtained. Recrystallized [Fe(bpp)2][NCS]2·2H2O and [Fe(bpp)2][NCSe]2 were identified as high spin with average Fe–N distances of 2.16 and 2.17 Å, respectively. In the unit cell of [Fe(bpp)2][NCSe]2·H2O·0.25 CH3NO2, there are four independent iron atoms, three identified as low spin and the fourth as high spin. All salts crystallize in a layer-type array involving edge-to-face and face-to-face aryl–aryl-type interactions. Hydrogen bonding between pyrazole >NH groups, anions and solvate molecules is observed. The structure of the uncoordinated ligand was also determined, the molecule being found in a planar arrangement with thecis–cis configuration for the pyrazolyl groups relative to the central pyridyl and the >NH group being at the N 2 atom. Hydrogen bonding involving the >NH groups leads to stepped stacks of molecules. The principal difference in the geometry of coordinated and free bpp molecules is a contraction in the angles about the interannular bridges in the chelate rings. [Fe(bpp)2][NCS]2·2H2O: triclinic, space group P1–, a 8.302(6), b 8.446(6), c 21.531(13) Å, a 78.78(5), b 82.80(5), g 89.85(4)˚, Z 2. [Fe(bpp)2][NCSe]2: triclinic, space group P1–, a 8.354(4), b 8.409(4), c 19.918(9) Å, a 87.02(3), b 83.15(3), g 88.86(3)˚, Z 2. [Fe(bpp)2][NCSe]2·H2O·0.25 CH3NO2: monoclinic, space group Pn, a 16.425(12), b 20.774(9), c 16.933(14) Å, b 90.91(4)˚, Z 8. Uncoordinated bpp: orthorhombic, space group Pna21, a 8.075(3), b 22.479(9), c 5.525(1) Å, b Z 4.

Iron(II) and nickel(II) bis(ligand) complexes of 6-(5-methyl-1,2,4-oxadiazol-3-yl)-2,2′-bipyridine (L) are described. The ligand field in the iron complex is close to that at the singlet ( 1 A1) ? quintet ( 5 T2) crossover and magnetic and Mössbauer spectral evidence indicates that a spin transition occurs in salts of the iron complex but is centred above room temperature. The structures of [FeL2] [CF3SO3]2.CH3CN and [NiL2] [BF4]2.CH3CN were determined and both are very similar to the structures of the corresponding terpyridine complexes. Spectroscopic data indicate that for the iron complex π-interaction between the metal and the ligand is less than that in the terpyridine system. [FeL2] [CF3SO3]2.CH3CN is monoclinic, space group P 21/c; a 8 . 232(5), b 25 . 273(10), c 17 . 306(10) Å, β 92 . 37(3)°, Z 4; [NiL2] [BF4]2.CH3CN is monoclinic, space group P 21/c; a 8 . 136(2), b 17 . 558(2), c 23 . 783(7) Å, β 109 . 32(1)°, Z 4.

Tris(ligand)iron(II) complexes of 2-(pyrazol-3-yl)pyridine (3ppH) and 3-(thiazol-2-yl)pyrazole (3tpH) undergo temperature-induced singlet (1A1) ⇔ quintet (5T2) transitions. The transition in [Fe(3ppH)3] [CF3SO3]2.2H2O is continuous and centred above room temperature while that in the anhydrous triflate salt is discontinuous and is centred below room temperature. The latter transition occurs via a thermal hysteresis loop of width 12 K, Tc↓ and Tc↑ being 229 and 241 K, respectively. The displacement of the transition to lower temperature in the anhydrous salt is believed to be associated with the loss of hydrogen bonding involving the uncoordinated pyrazole >NH group and solvate water. In [Fe(3tpH)2(3tp)] [ClO4].2H2O and [Fe(3tpH)2(3tp)] [BF4].2H2O (3tp is the deprotonated ligand) continuous transitions are observed, centred below room temperature. In these instances the displacement is consistent with the intrinsically weaker field of the bidentate system containing two five-membered heterocycles. Structural data were obtained for [Fe(3ppH)3][CF3SO3]2.2H2O, [Fe(3tpH)3] [BF4]2.1·5H2O and [Ni(3tpH)3] [BF4]2.2(3tpH). The average metal–nitrogen distances in the complexes are 1·97, 2·18 and 2·09 Å, severally. The large difference in the distances for the two iron complexes arises from the different ground states: a singlet for the 3ppH complex and a quintet for the 3tpH complex. In all three salts there is extensive hydrogen bonding involving the pyrazole >NH groups, the anions and the solvate molecules. [Fe(3ppH)3] [CF3SO3]2.2H2O: monoclinic, space group P21/c, a 12·33(1), b 24·44(1), c 12·55(1) Å, β 115·27(4)°, Z 4. [Fe(3tpH)3] [BF4]2.1·5H2O: monoclinic, space group C 2/c, a 41·56(2), b 16·418(3), c 18·154(7) Å, β 106·94(2)°, Z 8. [Ni(3tpH)3] [BF4]2.2(3tpH):P bcn, a 14·928(2), b 15·310 (3), c 17·882 (3) Å, Z 4.