J.A. Real

Critical temperature of the LIESST effect in iron(II) spin crossover compounds

Abstract The light-induced crossover in a series of iron(II) compounds has been investigated by irradiating the sample at 10 K with a Kr + laser coupled to an optical fiber within a SQUID cavity. The temperature dependence of the molar fraction of the light-induced metastable HS state has been recorded for 22 compounds. The critical LIESST temperature, T c (LIESST), has been defined as the temperature for which the light-induced HS information was erased in the SQUID cavity. The dependence of T c (LIESST) as a function of the thermal spin crossover temperature, T 1/2 , has been discussed. The effect of cooperation has been analyzed and the influence of horizontal and vertical displacements of the LS and HS potential wells has been discussed on the basis of the non-adiabatic multiphonon theory.

Direct monitoring of spin state in dinuclear iron(II) coordination compounds

So far there has been no direct method to determine the spin state of molecules in dinuclear iron(II) compounds. The molecular fractions of high-spin (HS) and low-spin (LS) species have been deduced from magnetic susceptibility and zero-field Mossbauer spectroscopy data irrespective of whether they belong to LS–LS, LS–HS and HS–HS pairs. However, the distinction of pairs becomes possible if Mossbauer measurements are carried out in an external magnetic field. The proposed method opens new possibilities in the study of spin crossover phenomena in dinuclear compounds.

Spin crossover in six-coordinate [Fe(L)2(NCX)2] compounds with L = DPQ = 2,3-bis-(2′-pyridyl)-quinoxaline, ABPT = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole and X = S, Se: synthesis, magnetic properties and single crystal studies

Abstract The iron(II) compounds of formulae [Fe(DPQ)2(NCS)2]·CO(CH)3)2(DPQ = 2,3-bis-(2′-pyridyl)-quinoxaline) (1) and [Fe(ABPT)2-(NCX)2] (ABPT = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) X = S (2) and Se (3) were synthesized and the crystal structure of 1 determined by X-ray diffraction methods. It crystallizes in the monoclinic system P2 1 /n, a = 12.057(2), b = 22.474(5), c = 15.004(7) A , β = 109.76(3)°, V = 3826 A 3 , Z = 4 and T = 293 K . The structure is made up of discrete [Fe(DPQ)2(NCS)2] units. Each metal atom is in a distorted FeN6 octahedral environment, the Feue5f8N bonds ranging from 2.013(8) A to 2.425(8) A. Variable-temperature magnetic susceptibility data in the temperature range 290–4.2 K revealed that 1 is high spin, in contrast to 2 and 3 which show a moderately cooperative high spin ↔ low spin (HS ↔ LS) transition, centred at T 1 2 = 186 K and 224 K for 2 and 3 respectively. The thermodynamic model of Slichter and Drickamer was applied to account for the magnetic data. The intermolecular interaction parameter, the enthalpy and entropy changes associated with the spin transition of 2 were estimated as Γ = 2.3 kJ mol−1, ΔH = 10.7 kJ mol−1 and ΔS = 58 J mol−1K−1 respectively.

Synthesis, crystal structure and magnetic properties of the chiral iron(II) chain [Fe(bpym)(NCS)2]n (bpym = 2,2′-bipyrimidine)

Abstract The iron(II) compound of formula [Fe(bpym)(NCS)2]n (bpym = 2,2′-bipyrimidine) has been synthesized and its crystal structure determined by X-ray diffraction methods. It crystallizes in the tetragonal P41 (No. 76) and P43 space groups, a = 8.849(2), c=16.486(3) A , V=1290.9(5) A 3 , Z=4, D c =1.699 g cm −3 , M r =330.2, F(000)=664, λ( Mo K α)=0.71073 A , μ( Mo K α)=14.8 cm −1 and T=295 K. A total of 2449 reflections was collected over the range 3≤2ϑ≤55°; of these, 1657 were unique and 1321 were considered as observed (13σ(I)) and used in the structural analysis. The final R and Rw residuals were 0.027 and 0.026, respectively. The structure is made up of chiral (Δ and Λ enantiomers crystallize in the same crop) chains of iron(II) atoms bridged by bis-chelating bpym, the electroneutrality being achieved by N-bonded thiocyanato groups in cis position. Each metal atom is in a distorted FeN6 octahedral environment, the Feue5f8N bonds ranging from 2.265(3) to 2.028(4) A . The intrachain metal-metal separation is 5.960(1) A. Variable-temperature magnetic susceptibility data in the temperatyre range 290–4.2 K show that the iron(II) is high-spin and interacts in an antiferromagnetic fashion, the relevant parameters being J=−3.5 cm −1 and g=2.12 ( H =−JΣ i=1 n S i · S i+1 with S i = S i+1 =2) . The magnitude of the exchange coupling compares well with that reported for other structurally characterized bpym-bridged iron(II) complexes.

Low-temperature structures of catena-(bipyrimidine-N,N')bis(thiocyanato)copper(II) and poly-(μ-bipyrimidine-N,N',N'',N''')tetrakis(thiocyanato)dicopper(II)

Compound (I), catena-poly[(2,2-bipyrimi dine-κ 2 ,N,N)copper(II)-bis-μ-(thiocyanato-κN:κS], [Cu(NCS) 2 (C 8 H 6 N 4 )] n , M r =337.9, monoclinic,C2/c, a=11.403 (2), b=13.943 (3), c=7.722 (2) A, β=93.93 (2) o , V=1224.9 (4) A 3 , Z=4, D x =1.832 g cm -3 , λ(Mo Kα)=0.71069 A, μ=21.1 cm -3 , F(000)=676, T=153 K, final R=0.025 and wR=0.032 for 1241 reflections with I>3 σ(I)

Determination of spin state in dinuclear iron(II) coordination compounds using applied field Mossbauer spectroscopy

So far there has been no direct method to determine the spin state of molecules in dinuclear iron(II) compounds. The molecular fractions of high spin (HS) and low spin (LS) species have been deduced from magnetic susceptibility and zero field Mössbauer spectroscopy data irrespective of whether they belong to LS-LS, LS-HS and HS-HS pairs. However, the distinction of pairs becomes possible if Mössbauer measurements are carried out in an external magnetic field. The proposed method opens new possibilities in the study of spin crossover phenomena in dinuclear compounds.

Evaluation of the Effectiveness of a Psychoeducational Intervention in Treatment-Naïve Patients with Antidepressant Medication in Primary Care: A Randomized Controlled Trial.

Background. There is evidence supporting the effectiveness of psychoeducation (PE) in patients with symptoms of depression in primary care (PC), but very few studies have assessed this intervention in antidepressant-naïve patients. The aim of this study is to assess the effectiveness of a PE program in these patients, since the use of antidepressant (AD) medication may interfere with the effects of the intervention. Methods. 106 participants were included, 50 from the PE program (12 weekly 1.5-hour sessions) and 56 from the control group (CG) that received the usual care. Patients were assessed at baseline and at 3, 6, and 9 months. The main outcome measures were the Beck Depression Inventory (BDI) and remission based on the BDI. The analysis was carried out on an intention-to-treat basis. Results. The PE program group showed remission of symptoms of 40% (P = 0.001) posttreatment and 42% (P = 0.012) at 6 months. The analysis only showed significant differences in the BDI score posttreatment (P = 0.008; effect size Cohens d′ = 0.55). Conclusions. The PE intervention is an effective treatment in the depressive population not treated with AD medication. Before taking an AD, psychoeducational intervention should be considered.