Two mononuclear complexes [(Et 3 NH)[M(hfac) 2 L] (M = Ni, 1 Zn, 2) have been synthesized using a nitronyl-nitroxide radical substituted nitrophenol, i.e., 2-(2-Hydroxy-3-methoxy-5nitrophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl, HL, as a proligand. The crystal structures of the two compounds have been solved and indicate an octahedral coordination geometry of the metal ions. The magnetic behavior for compound 1is characterized by a strong antiferromagnetic metal-radical interaction (J = -351 ± 1 cm -1 ; H = -JS Ni S Rad ). This exchange interaction was rationalized by DFT calculations. The EPR spectra recorded both in solution and solid state at 120 K confirm the S = ½ ground state for compound 1.
Five binuclear complexes with rectangular topology have been synthesized using a nitronyl‐nitroxide ligand (L) functionalized with a pyrazole coordinating group: [Ln2(hfac)2L2], with Ln=Eu (1), Gd (2 a, 2 b), Tb (3), Dy (4), Tm (5). The EuIII and TmIII complexes crystallize in the P21/n space group, while the GdIII, TbIII, and DyIII derivatives crystalize in P‐1 space group. The crystal structures for compounds 2 a, 3, 4, and 5 have been fully solved, while for compounds 1 and 2 b, the unit cell parameters have been measured and compared with crystals 3 and 5. Crystals 2 a (P21/n) and 2 b (P‐1) are polymorphic forms. In these complexes the nitronyl‐nitroxide ligand bridges two metal ions through one aminoxyl group and the pyrazole fragment. In the five complexes the LnIII ions show a coordination number of eight with a triangular dodecahedron geometry. The magnetic properties of all five complexes have been investigated. For compounds 2, 3, and 4 the LnIII‐Rad interaction was found to be ferromagnetic: JGdRad=2.09(1) cm−1 [H=‐2JGdRad(SGd1SRad1+SGd2SRad2], JTbRad=1.93(14) cm−1, JDyRad=1.72(14) cm−1. The TmIII‐Rad coupling is antiferromagnetic (JTmRad=−0.53(1) cm−1). For the TbIII, DyIII, and TmIII complexes the effects of the crystal field have been taken into account in the fitting procedure.
Synthesis, crystal structures and solid-state optical properties of two Mannich derivatives of 2',7'dichlorofluorescein are reported herein. The first derivative (MBFluo1), resulted by Mannich reaction from 2',7'-dichlorofluorescein, paraformaldehyde and N-methylpiperazine, crystallizes in a zwitterionic form, while the second derivative (MBFluo2) was obtained in the non-charged spironolactone form from 2',7'-dichlorofluorescein, paraformaldehyde and di-tert-buthyliminodiacetate. The emission spectra of MBFluo2 present two maxima at 420 and 550 nm.
A new nitronyl‐nitroxide ligand (H2L) featuring alcoholic and phenolic groups has been synthesised starting from 2‐hydroxy‐3‐(hydroxymethyl)‐5‐methylbenzaldehyde (A). Using this ligand, three 2p–4 f binuclear complexes have been obtained and crystallographically characterized: [Ln2(HL)2(hfac)4], (Ln=Gd 1, Tb 2, Dy 3). Apart from the desired compounds, two by‐products have been isolated as a molecular alloy containing an intermediate bearing hydroxylamino and N‐oxide groups, i. e. (1‐hydroxy‐2‐(2‐hydroxy‐3‐(hydroxymethyl)‐5‐methylphenyl)‐4,4,5,5‐tetramethyl‐4,5‐dihydro‐1H‐imidazole 3‐oxide, B, and the imino‐nitroxide derivative, C. This system was characterized by single crystal X‐ray diffraction, UV‐VIS and EPR spectroscopy. During the synthesis of compounds 1–3, two other complexes have been obtained and characterized: [Ln(C)(hfac)3] (4, Ln=Tb) and [Ln2(A−H)2(hfac)4] (5, Ln=Tb), where (A−H) results from the deprotonation of the phenolic group in A. The synthetic procedure was optimized in order to obtain pure 1–3 complexes. The cryomagnetic properties of compounds 1–3 have been investigated. Continuous‐wave (CW) electron paramagnetic resonance (EPR) measurements were carried out at X‐ and Q‐band for compound 1. Time‐dependent experiments were performed at three magnetic fields. Phase memory times, Tm, were found to be about 1000 ns at 6 K.
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