Functional insulin therapy in type 1 diabetics: Short-term effects on weight and nutritional intake.

INTRODUCTION-AIM: Flexible insulin therapy is currently considered the gold standard therapy of type 1 diabetes. We aimed to study the evolution of glycemic control, weight and nutritional intake of a group of patients with type 1 diabetes, three months after the initiation of functional insulin therapy (FIT). METHODS: This was a prospective longitudinal study having included 30 type 1 diabetic patients hospitalized for education to FIT. Each patient underwent an assessment of glycemic control (glycated hemoglobin (A1C) and number of hypoglycemia), weight and nutritional intake before FIT and 3 months after the initiation of this educative approach. RESULTS: The mean age of patients was 21,8 ± 7,9 years and the sex ratio was 0,5. The mean duration of diabetes was 7,2 ± 6 years. Three months after initiation of FIT, we observed a significant lowering of A1C, which went from 9,2 ± 1,6% to 8,3 ± 1,4% (p<0,001) of the number of minor hypoglycemia (p=0,001) and that of severe hypoglycemia (p= 0,021). the average weight went from 64,6 ± 13,1 kg to 65,5 ± 13,5 kg (p = 0,040) with a significant increase in BMI (p = 0,041). Weight gain was observed in 67% of patients. This weight gain contrasted with a significant decrease in caloric (p = 0,040) and in carbohydrates intakes (p = 0,027). CONCLUSION: Weight gain, associated with better glycemic control, should encourage the healthcare team to strengthen therapeutic education of patients undergoing FIT in order to limit weight gain.

Capturing electron-driven chiral dynamics in UV-excited molecules.

Chiral molecules, used in applications such as enantioselective photocatalysis1, circularly polarized light detection2 and emission3 and molecular switches4,5, exist in two geometrical configurations that are non-superimposable mirror images of each other. These so-called (R) and (S) enantiomers exhibit different physical and chemical properties when interacting with other chiral entities. Attosecond technology might enable influence over such interactions, given that it can probe and even direct electron motion within molecules on the intrinsic electronic timescale6 and thereby control reactivity7-9. Electron currents in photoexcited chiral molecules have indeed been predicted to enable enantiosensitive molecular orientation10, but electron-driven chiral dynamics in neutral molecules have not yet been demonstrated owing to the lack of ultrashort, non-ionizing and perturbative light pulses. Here we use time-resolved photoelectron circular dichroism (TR-PECD)11-15 with an unprecedented temporal resolution of 2.9 fs to map the coherent electronic motion initiated by ultraviolet (UV) excitation of neutral chiral molecules. We find that electronic beatings between Rydberg states lead to periodic modulations of the chiroptical response on the few-femtosecond timescale, showing a sign inversion in less than 10 fs. Calculations validate this and also confirm that the combination of the photoinduced chiral current with a circularly polarized probe pulse realizes an enantioselective filter of molecular orientations following photoionization. We anticipate that our approach will enable further investigations of ultrafast electron dynamics in chiral systems and reveal a route towards enantiosensitive charge-directed reactivity.

X-ray crystallographic analysis of the antiferromagnetic low-temperature phase of galvinoxyl: investigating magnetic duality in organic radicals.

Galvinoxyl, as one of the most extensively studied organic stable free radicals, exhibits a notable phase transition from a high-temperature (HT) phase with a ferromagnetic (FM) intermolecular interaction to a low-temperature (LT) phase with an antiferromagnetic (AFM) coupling at 85 K. Despite significant research efforts, the crystal structure of the AFM LT phase has remained elusive. This study successfully elucidates the crystal structure of the LT phase, which belongs to the P1̄ space group. The crystal structure of the LT phase is found to consist of a distorted dimer, wherein the distortion arises from the formation of short intermolecular distances between anti-node carbons in the singly-occupied molecular orbital (SOMO). Starting from the structure of the LT phase, wave function calculations show that the AFM coupling 2J/kB varies significantly from -1069 K to -54 K due to a parallel shift of the molecular planes within the dimer.

Modifications of Tanabe-Sugano d6 Diagram Induced by Radical Ligand Field: Ab Initio Inspection of a Fe(II)-Verdazyl Molecular Complex.

Quantum entanglement between the spin states of a metal center and radical ligands is suggested in an iron(II) [Fe(dipyvd)2]2+ compound (dipyvd = 1-isopropyl-3,5-dipyridil-6-oxoverdazyl). Wave function ab initio (Difference Dedicated Configuration Interaction, DDCI) inspections were carried out to stress the versatility of local spin states. We named this phenomenon excited state spinmerism, in reference to our previous work (see Roseiro et al., ChemPhysChem 2022, e202200478) where we introduced the concept of spinmerism as an extension of mesomerism to spin degrees of freedom. The construction of localized molecular orbitals allows for a reading of the wave functions and projections onto the local spin states. The low-energy spectrum is well-depicted by a Heisenberg picture. A 60 cm-1 ferromagnetic interaction is calculated between the radical ligands with the Stotal = 0 and 1 states largely dominated by a local low-spin SFe = 0. In contrast, the higher-lying Stotal = 2 states are superpositions of the local SFe = 1 (17%, 62%) and SFe = 2 (72%, 21%) spin states. Such mixing extends the traditional picture of a high-field d6 Tanabe-Sugano diagram. Even in the absence of spin-orbit coupling, the avoided crossing between different local spin states is triggered by the field generated by radical ligands. This puzzling scenario emerges from versatile local spin states in compounds which extend the traditional views in molecular magnetism.

Development and validation of anthropometric predictive equations that estimate the total body water and fat-free mass in Tunisian adults.

OBJECTIVE: To develop and validate equations that estimate total body water (TBW) and fat-free mass (FFM) in adults using anthropometric measurements. METHODS: A cross-sectional study was conducted among 178 adults (77 men and 101 women; aged 18-59 years). Participants were distributed by sex and age groups, and then randomly assigned to equal two groups; the development (n = 89) and the validation (n = 89). The anthropometric measurements included height and weight. The deuterium dilution technique (DDT) estimated TBW and FFM. Linear regression models were used with the TBW and FFM as the dependent variable, and height and weight as the independent variables. Cross-validation was performed by Bland and Altman plot, and the new anthropometric equations were developed. RESULTS: In the validation sample, the developed equations had high R2 of 94.4 for both TBW and FFM in all age groups, and low standard errors (RMSE: 1.80 kg for TBW and 2.44 kg for FFM). The pure error was 2.03 for the TBW equation and 2.71 for the FFM equation. The Bland-Altman plot illustrated the good level of concordance between the TBW and FFM predicted by the new equations as determined by DDT. The following developed equations showed a better agreement with the DDT: [Formula: see text]; [Formula: see text]. CONCLUSION: In this study, we developed and validated prediction equations for the estimation of TBW and FFM from DDT in healthy adult Tunisian population. The newly anthropometric prediction equations seem to be the most accurate for Tunisian adult.

A clinical trial about effects of prebiotic and probiotic supplementation on weight loss, psychological profile and metabolic parameters in obese subjects.

INTRODUCTION: The management of obesity is difficult with many failures of lifestyle measures, hence the need to broaden the range of treatments prescribed. The aim of our work was to study the influence of pre and probiotics on weight loss psychological profile and metabolic parameters in obese patients. METHODS: It is a clinical trial involving 45 obese patients, recruited from the Obesity Unit of the National Institute of Nutrition between March and August 2022 divided into three groups: diet only (low-carbohydrate and reduced energy diet), prebiotics (30 g of carob/day) and probiotics (one tablet containing Bifidobacterium longum, Lactobacillus helveticus, Lactococcus lactis, Streptococcus thermophilus/day). The three groups were matched for age, sex and BMI. Patients were seen after 1 month from the intervention. Anthropometric measures, biological parameters, dietary survey and psychological scores were performed. RESULTS: The average age of our population was 48.73 ± 7.7 years, with a female predominance. All three groups showed a significant decrease in weight, BMI and waist circumference with p < .05. Only the prebiotic and probiotic group showed a significant decrease in fat mass (p = .001) and a significant increase in muscle strength with p = .008 and .004, but the differences were not significant between the three groups. Our results showed also a significant decrease in insulinemia and HOMA-IR in the prebiotic group compared to the diet-alone group (p = .03; p = .012) and the probiotic group showed a significant decrease in fasting blood glucose compared to the diet alone group (p = .02). A significant improvement in sleep quality was noted in the prebiotic group (p = .02), with a significant decrease in depression, anxiety and stress in all three groups. CONCLUSIONS: The prescription of prebiotics and probiotics with the lifestyle measures seems interesting for the management of obesity especially if it is sarcopenic, in addition to the improvement of metabolic parameters and obesity-related psychiatric disorders.

Cross sectional study about nutritional risk factors of metabolically unhealthy obesity.

INTRODUCTION: A substantial proportion of obese subjects are metabolically healthy and free from metabolic complications. Many mechanisms that could explain the existence of the metabolically healthy obese phenotype have been suggested, involving in particular a healthy lifestyle and diet. The aim of this study was to study the anthropometric, nutritional and biological profile of two groups: obese with metabolic syndrome (MS+) and obese without metabolic syndrome (MS-). METHODS: It is a cross-sectional study, conducted between January 2022 and 15 March 2022. We recruited 90 obese MS+ and 82 obese MS - . Both groups were matched for age and sex. The glycemia, triglycerides (TG), total cholesterol (TC), HDL-C, LDL-C were measured as well as the body composition and anthropometric data. The diet was determined by the 24-hour recalls. Eating disorders, sleep disorders (PSS4 scale) and depression (HADS) were also searched. RESULTS: In MS+ group we noticed: higher BMI, waist circumference, more caloric diet, elevated consumption of saccharides. This group had more eating disorders such as night eating syndrome and bulimia and sleeping disorders (sleep onset and total insomnia). MS + group was more stressed and depressed. The MS - group had a Mediterranean diet and had more intake of: EPA, DHA, olive oil, green tea, oleaginous fruits, linseed, vegetables and whole grains. They also practiced more fasting. CONCLUSIONS: It is important to know the protective nutritional factors of the metabolic syndrome in order to be able to focus on them during education sessions and thus protect the obese from metabolic complications.

Vitamin Status of Obese Tunisian adults before and after Sleeve Gastrectomy.

INTRODUCTION: The worldwide obesity epidemic continues unabated. Obesity and its associated health risks are considered as the major causes of morbidity and mortality. Currently, bariatric surgery is the most effective treatment for people with severe obesity resulting in sustainable weight loss and a reduced risk for co-morbidities. Sleeve gastrectomy is the most common bariatric procedure undertaken in Tunisia. AIM: we aim to evaluate the vitamin status of the obese patients before and after sleeve gastrectomy. METHODS: Thirty obese patients undergoing sleeve gastrectomy, were recruited from Obesity unit. In this study. A biological assessment was performed pre-operatively and controlled 6 months following the sleeve gastrectomy including: calcemia, parathyroid hormone (PTH), albuminemia and dosage of vitamin D, vitamin B9 and vitamin B12. RESULTS: Six months post sleeve gastrectomy, vitamin deficiencies were more prevalent: the mean level of vitamin B9, vitamin B12 and vitamin D respectively, has decreased from 5.03±3.28 ng / ml to 2.71±1.52 ng / ml, from 348.06±158.92 pg/ml to 264.62±119.77 pg/ml and from 17.18±11.45 ng/ml to 11.69±8.22 ng/ml, with a statistically significant difference (p=0.008, p=0.01 and p=0.012). Sleeve gastrectomy has proven to be an effective weight loss treatment. However, nutritional deficiencies have worsened during postoperative period. CONCLUSION: This study highlights the importance of early identification, appropriate treatment and prophylactic micronutrient supplementation.

Difficulty of the evaluation of the barrier height of an open-shell transition state between closed shell minima: The case of small C4n rings.

C4n cyclacenes exhibit strong bond-alternation in their equilibrium geometry. In the two equivalent geometries, the system keeps an essentially closed-shell character. The two energy minima are separated by a transition state suppressing the bond-alternation, where the wave function is strongly diradical. This paper discusses the physical factors involved in this energy difference and possible evaluations of the barrier height. The barrier given as the energy difference between the restricted density functional theory (DFT)/B3LYP for the equilibrium and the broken symmetry DFT/B3LYP of the transition state is either negative or small, in contradiction with the most reliable Wave Function Theory calculations. The minimal (two electrons in two molecular orbitals) Complete Active Space self-consistent field (CASSCF) overestimates the barrier, and the subsequent second-order perturbation cancels it. Due to the collective character of the spin-polarization effect, it is necessary to perform a full π CASSCF + second-order perturbation to reach a reasonable value of the barrier, but this type of treatment cannot be applied to large molecules. DFT procedures treating on an equal foot the closed-shell and open-shell geometries have been explored, such as Mixed-Reference Spin-Flip Time-dependent-DFT and a new spin-decontamination proposal, namely, DFT-dressed configuration interaction, but the results still depend on the density functional. M06-2X without or with spin-decontamination gives the best agreement with the accurate wave function results.

Is fat taste associated with diet quality? A cross-sectional study conducted among Tunisian adults.

The Tunisian population has experienced a nutrition transition with an increase in the incidence of obesity. As obesity has been associated with a poor orosensory detection of fat. We hypothesized that poor fat detection could be a driver of poor diet quality. This study examined the association between linoleic acid (LA) detection and adherence to a healthy diet among adult participants. A total of 104 LA taster participants were recruited for this study. Dietary assessment was conducted using the 24 h dietary recall method. Diet quality was assessed by determining the Mediterranean diet (MD) score and Health diet indicator (HDI). The relationship between diet quality and log LA detection threshold was done using adjusted linear regression for age, sex, and daily energy intake (only in the fully adjusted model). The predictive margins model (interaction: anthropometric status x LA threshold) was used to assess the difference between non-obese and subjects with obesity adherence to MD across LA detection values. We have observed that the increase in the concentration of linoleic acid detection by 1 log(mmol/L) is associated with an increase of HDI score by 0.12-point [95% CI: 0.02-0.21] and a decrease of the MD score by -0.14-point [-0.25 to -0.03] in the partially adjusted model. However, only the MD score remained negatively associated with LA detection threshold in the fully adjusted model. The subjects with obesity adherence to the Mediterranean diet was lower than subjects with normal weight for LA concentration less than 0 log(mmol/L). The present study suggests that poor orosensory detection of dietary lipids might be a driver for worsening diet quality. Hence, These subjects might be at risk for obesity and, consequently, exposed cumulatively to the harmful effects of excess adiposity and an unhealthy diet.

The Role of Dietary Intake in Type 2 Diabetes Mellitus: Importance of Macro and Micronutrients in Glucose Homeostasis.

The prevalence of Type 2 diabetes (T2D) is increasing worldwide. Genetics and lifestyle, especially diet, are contributing factors. Analyses of macro- and micronutrient intake across global populations may help to explain their impact on glucose homeostasis and disease development. To this end, 420 Tunisians were enrolled in a prospective cross-sectional study of daily food consumption. Various data were collected and blood samples were drawn for biochemical assay. A 24-h recall questionnaire was obtained from participants to evaluate dietary intake. Statistical analyses were conducted using Nutrilog and R software. Biochemical analyses stratified the studied population (n = 371) into three groups: diabetics (n = 106), prediabetics (n = 192) and controls (n = 73); 49 subjects were excluded. Our results showed that Tunisians had hypercaloric diets high in carbohydrates and fat with variability in the levels of some vitamins and minerals, including riboflavin and niacin, that were statistically different among groups. The lower intake of vitamin D was associated with a greater risk of T2D. Higher vitamin A and sodium intake were associated with poor glucose homeostasis, although protein intake may improve it. In perspective, nutrigenomic studies can provide insight into problematic diets and poor eating habits and offer opportunities to analyze the effects of behavioral changes that can mitigate T2D development and progression.

Combining Open-Shell Verdazyl Environment and Co(II) Spin-Crossover: Spinmerism in Cobalt Oxoverdazyl Compound.

The spin states of a Co(II) oxoverdazyl compound are investigated by means of wavefunction-based calculations. Within a ca. 233 K energy window, the ground state and excited states display a structure-sensitive admixture of low-spin SM =1/2 in a dominant high-spin SM =3/2 Co(II) ion as indicated by the localized molecular orbitals. The puzzling spin zoology that results from the coupling between open-shell radical ligands and a spin-crossover metal ion gives rise to this unusual scenario, which extends the views in molecular magnetism. In agreement with experimental observation, the low-energy spectroscopy is very sensitive to deformations of the coordination sphere, and a growing admixture of Co(II) low-spin is evidenced from the calculations. In analogy with mesomerism that accounts for charge delocalization, entanglement combines different local spin states to generate a given total spin multiplicity, a spinmerism phenomenon.

Plasmatic Magnesium Deficiency in 101 Outpatients Living with Type 2 Diabetes Mellitus.

(1) Background: Magnesium deficiency is usually associated with type 2 diabetes mellitus (T2DM). Individuals living with T2DM with hypomagnesemia show a more rapid disease progression and have an increased risk for diabetes complications. (2) Methods: This is a cross-sectional and descriptive study in the National Institute of Nutrition and Food Technology of Tunis in Tunisia, including all adult outpatients (≥18 years old) with a diagnosis of T2DM from 1 September 2018 to 31 August 2019. The aim of this study was to evaluate the prevalence of plasmatic magnesium deficiency in a Tunisian population of T2DM and to study the relationship between magnesium status and intake, glycemic control and long-term diabetes-related complications. (3) Results: Among the 101 T2DM outpatients, 13 (12.9%) presented with a plasmatic magnesium deficiency. The mean age was 56 ± 7.9 years with a female predominance (62%, n = 63). The mean of the plasmatic magnesium level was 0.79 ± 0.11 mmol/L (0.5-1.1), and the mean of 24 h urinary magnesium excretion was 87.8 ± 53.8 mg/24 h [4.8-486.2]. HbA1c was significantly higher in the plasmatic magnesium deficiency group than the normal magnesium status group (10% ± 1.3 vs. 8.3% ± 1.9; p = 0.04), with a significant difference in participants with a poor glycemic control (HbA1c > 7%) (100%, n = 13/13 vs. 53%, n = 47/88; p = 0.001). A weak negative relationship was also found between plasmatic magnesium and HbA1c (r = -0.2, p = 0.03). Peripheral artery disease was more commonly described in individuals with low plasmatic magnesium levels than in individuals with normal levels (39%, n = 5 vs. 0%, n = 0; p < 0.001). The mean plasmatic magnesium level in participants without diabetic nephropathy and also peripheral artery disease was significantly higher compared to individuals with each long-term diabetes-related complication (0.8 mmol/L ± 0.1 vs. 0.71 mmol/L ± 0.07; p = 0.006) and (0.8 mmol/L ± 0.1 vs. 0.6 mmol/L ± 0.08; p < 0.001), respectively. (4) Conclusions: Hypomagnesemia was identified in individuals with T2DM, causing poor glycemic control and contributing to the development and progression of diabetes-related microvascular and macrovascular complications.

Model protein excited states: MRCI calculations with large active spaces vs CC2 method.

Benchmarking calculations on excited states of models of phenylalanine protein chains are presented to assess the ability of alternative methods to the standard and most commonly used multiconfigurational wave function-based method, the complete active space self-consistent field (CASSCF), in recovering the non-dynamical correlation for systems that become not affordable by the CASSCF. The exploration of larger active spaces beyond the CASSCF limit is benchmarked through three strategies based on the reduction in the number of determinants: the restricted active space self-consistent field, the generalized active space self-consistent field (GASSCF), and the occupation-restricted multiple active space (ORMAS) schemes. The remaining dynamic correlation effects are then added by the complete active space second-order perturbation theory and by the multireference difference dedicated configuration interaction methods. In parallel, the approximate second-order coupled cluster (CC2), already proven to be successful for small building blocks of model proteins in one of our previous works [Ben Amor et al., J. Chem. Phys. 148, 184105 (2018)], is investigated to assess its performances for larger systems. Among the different alternative strategies to CASSCF, our results highlight the greatest efficiency of the GASSCF and ORMAS schemes in the systematic reduction of the configuration interaction expansion without loss of accuracy in both nature and excitation energies of both singlet ππ* and nπ* CO excited states with respect to the equivalent CASSCF calculations. Guidelines for an optimum applicability of this scheme to systems requiring active spaces beyond the complete active space limit are then proposed. Finally, the extension of the CC2 method to such large systems without loss of accuracy is demonstrated, highlighting the great potential of this method to treat accurately excited states, mainly single reference, of very large systems.

Impact of nutrients and Mediterranean diet on the occurrence of gestational diabetes.

Background: The Mediterranean diet (MedDiet) is a dietary pattern effective in terms of prevention of many diseases such as gestational diabetes mellitus (GDM). Recently, many studies have paid attention to nutritional factors during pregnancy as a modifiable contributor to GDM risk.Objective: to investigate associations of nutrients intakes and MedDiet pattern of eating with risk of GDM.Subjects/Methods: This study conducted on N = 120; Pregnant women with GDM (n = 60) and without controls (n = 60). The dietary habits were assessed by a dietary history method and a validated food frequency questionnaire. We calculated a MedDiet score which measures the degree of adherence to a Med Diet.Result: A low Med Diet score was found in pregnant women with and without gestational diabetes in 46.7% and 38.8% of cases, respectively, with no significant difference. Our data showed that the higher the adherence score to the MedDiet, the lower the fasting blood glucose level and the plasma glucose 2 h post load. These findings concerned the two groups studied (P < 10-3). We also noted that controls had a significantly higher intake of legumes, vegetables and fish. Monounsaturated fatty acids and saturated fatty acids consumption was significantly higher in the control group (2.3 ± 0.8 vs 1.7 ± 0.7, P < 10-3). GDM subjects consumed significantly more dairy products and cereals (P < 10-3). After adjustment for confounders, no nutrient was associated with the risk of developing gestational diabetes except vitamin D intake (OR 0.29 [0.15-0.54], P < 10-3) which had a protective effect.Conclusion: Our study underlines the importance of adequate vitamin D intake during pregnancy and suggests that the MedDiet may reduce the incidence of gestational diabetes.

Impact of sleeve gastrectomy on abnormalities in carbohydrate tolerance in obese adult.

INTRODUCTION: Facing the repeated failures of the medical management of obesity, bariatric surgery offers a promising therapeutic option in terms of achieving weight loss and metabolic benefits. AIM: To evaluate the impact of sleeve gastrectomy on the carbohydrate profile of a group of obese subjects. METHODS: It is a prospective study including 40 obese patients (7 Men and 33 Women) who underwent sleeve gastrectomy between 2016 and 2018. Clinical and biological parameters were collected before the intervention, at six months and one year after. Insulin resistance was defined by a HOMA-IR index ≥2.4. Remission of diabetes was determined using the American Society for Metabolic and Bariatric Surgery's (ASMBS) criteria. RESULTS: The mean patients' age was 34.65 ± 8.17 years. The mean body mass index (BMI) was 50.23 ± 8.3 kg/m². One year after sleeve gastrectomy, the frequency of insulin resistance, decreased from 89% to 4% (p<0.05). The evolution of carbohydrate tolerance abnormalities was marked by the diabetes and prediabetes remission in 75% and 100% of cases, respectively. The mean excess weight loss was 55.8% at 12 months. CONCLUSION: These results have expanded our knowledge of the short-term sleeve gastrectomy's effectiveness on the carbohydrate profile of obese subjects. However, it would be interesting to check the durability of this metabolic benefit in the medium and long term.

Sardinelle protein isolate as a novel material for oil microencapsulation: Novel alternative for fish by-products valorisation.

The present study investigates the potential of sardinelle protein isolate (SrPI) combined to maltodextrin (MD), at different ratios (1:0, 1:1, 1:2, 1:3 and 1:4, w/w), as wall matrix to stabilize and encapsulate corn oil (1:2, oil/ wall material ratio). Emulsions were prepared by homogenization followed by sonication treatment and then dried by the spray-drying process. The obtained microcapsules were characterized regarding the encapsulation efficiency (EE), scanning electron microscopy (SEM), infrared spectroscopy (FTIR), and thermodynamic analyses (thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC)). Data revealed that the combination of SrPI and MD resulted in very high EE compared to SrPI used alone as wall material, and the EE increased with the amount of MD incorporated to the SrPI solution. SEM images showed the production of irregular and larger particles with the increase of MD concentration. Moreover, TGA showed that microparticles obtained by 1:4 w/w ratio (SrPI/MD) displayed the highest protection of corn oil. Thus, these findings revealed the effectiveness of SrPI and MD mixture to encapsulate and protect corn oil, which offered a promote application for food and pharmaceutical industries.

Spin polarization as an electronic cooperative effect.

Taking as an example the simple CH3 radical, this work demonstrates the cooperative character of the spin-polarization phenomenon of the closed-shell core in free radicals. Spin polarization of CH σ bonds is not additive here, as spin polarization of one bond enhances that of the next bond. This cooperativity is demonstrated by a series of configuration interaction calculations converging to the full valence limit and is rationalized by analytic developments. The same phenomenon is shown to take place in those diradicals where spin polarization plays a major role, as illustrated in square planar carbo-cyclobutadiene C12H4. The treatment of cooperativity represents a challenge for usual post-Hatree-Fock methods.

Origin of Ferromagnetism and Magnetic Anisotropy in a Family of Copper(II) Triangles.

Previously reported ferromagnetic triangles (NnBu4 )2 [Cu3 (µ3 -Cl)2 (µ-4-NO2 -pz)3 Cl3 ] (1), (PPN)2 [Cu3 (µ3 -Cl)2 (µ-pz)3 Cl3 ] (2), (bmim)2 [Cu3 (µ3 -Cl)2 (µ-pz)3 Cl3 ] (3) and newly reported (PPh4 )2 [Cu3 (µ3 -Cl)2 (µ-4-Ph-pz)3 Cl3 ] (4) were studied by magnetic susceptometry, electron paramagnetic resonance (EPR) spectroscopy and ab initio calculations to assess the origins of their ferromagnetism and of the magnetic anisotropy of their ground S=3/2 state (PPN+ =bis(triphenylphosphine)iminium, bmim+ =1-butyl-3-methylbenzimidazolium, pz- =pyrazolate). Ab initio studies revealed the d z 2 character of the magnetic orbitals of the compressed trigonal bipyramidal copper(II) ions. Ferromagnetic interactions were attributed to weak orbital overlap via the pyrazolate bridges. From the wavefunctions expansions, the ratios of the magnetic couplings were determined, which were indeterminate by magnetic susceptometry. Single-crystal EPR studies of 1 were carried out to extend the spin Hamiltonian with terms which induce zero-field splitting (zfs), namely dipolar interactions, anisotropic exchange and Dzyaloshinskii-Moriya interactions (DMI). The data were treated through both a giant-spin model and through a multispin exchange-coupled model. The latter indicated that ≈62 % of the zfs is due to anisotropic and ≈38 % due to dipolar interactions. The powder EPR data of all complexes were fitted to a simplified form of the multispin model and the anisotropic and dipolar contributions to the ground state zfs were estimated.