Structural isomerism-tuned magnetisation relaxation dynamics in lanthanide coordination complexes

The eigenspectrum and eigenvectors of the 2F7/2 ground multiplets of two structural isomer coordination complexes, Yb(trenovan) (H3trenovan = tris(((3-methoxysaliclidene)amino)ethyl)amine) and Yb(trenpvan) (H3trenpvan = tris(((5-methoxysaliclidene)amino)ethyl)amine), were determined by use of magnetometry and electron paramagnetic resonance and luminescence spectroscopies. The two 4f complexes crystallise in the trigonal 3̅ space group, have identical chemical formulas and differ only in the placement of the methoxy group on the aromatic ring of salicylaldehyde, with it being either ortho, Yb(trenovan), or para, Yb(trenpvan), to the phenoxo group. This structural isomerism is found to have a profound influence on the solid state static and dynamic magnetic properties of the complexes. In the bulk, both isomers display a combination of direct and raman magnetisation relaxation procceses, however, at vastly different rates. Magnetic dilution in an isostructural diamagnetic host supresses the occurrence of the direct procces suggesting that the direct process observed in the bulk originates from Yb(III) centres coupled by magnetic dipole interactions. The eigenspectrum, eigenvectors and spin lattice relaxation of Yb(trenpvan) are found to be closer to the ones found in Yb(trensal) (H3trensal = tris(((saliclidene)amino)ethyl)amine) where the methoxy group is substituted by an H atom, than to those of Yb(trenovan) where the methoxy group is in the ortho position. Thus, the position of chemical modifications has a tremendous influence on the static and dynamic solid state magnetic properties of 4f coordination complexes. Our detailed study on single crystals, demonstrates that the rarely studied effect of modifications of the position of second coordination sphere chemical groups on the dynamic magnetic properties can in fact be used to chemically tune the magnetisation dynamics of 4f spin systems

Long Aliphatic Chain Derivatives of Trigonal Lanthanide Complexes

The trigonal lanthanide complexes LnL (H3L = tris(((3-formyl-5-methylsalicylidene)amino)ethyl)amine) contain three pendant aldehyde groups and are known to react with primary amines. Reacting LnL (Ln = Yb, Lu) with 1-octadecylamine yields the novel aliphatic lanthanide complexes LnL18 (H3L18 = tris(((3-(1-octadecylimine)-5-methylsalicylidene)amino)ethyl)amine) where the three aldehyde groups are transformed to 1-octadecylimine groups. Herein the syntheses, structural characterisation and magnetic properties of LnL18 are presented. The crystal structure of YbL18 shows that the reaction of YbL with 1-octadecylamine leads to only very subtle perturbations in the first coordination sphere of Yb(III), with the Yb(III) ion retaining its heptacoordination and similar bond lengths and angles to the ligand. The three octadecyl chains in each complex were found to direct crystal packing into lipophilic arrays of van-der-Waals interaction-driven hydrocarbon stacking. The static magnetic properties of YbL18 were compared to those of the non-derivatised complex YbL. The energy level splitting of the 2F7/2 ground multiplet was found, by emission spectroscopy, to be very similar between the derivatised and non-derivatised complexes. A.c. magnetic susceptibility measurements on YbL18 and YbL diluted at 4.8 % and 4.2 % into the diamagnetic hosts LuL18 and LuL, respectively, revealed that the spin-lattice relaxation of both complexes is governed by a low temperature direct process and a high temperature Raman process. In the high temperature regime, the derivatised complex was also found to have faster spin-lattice relaxation, which is likely due to the increased number of phonons in the octadecyl chains

Design of Pure Heterodinuclear Lanthanoid Cryptate Complexes

Heterolanthanide complexes are difficult to synthesize owing to the similar chemistry of the lanthanide ions. Conse-quently, very few purely heterolanthanide complexes have been synthesized. This is despite the fact that such complexes hold inter-esting optical and magnetic properties. To fine-tune these properties, it is important that one can choose complexes with any given combination of lanthanides. Herein we report a synthetic procedure which yields pure heterodinuclear lanthanide cryptates LnLn*LX3 (X = NO3- or OTf-) based on the cryptand H3L = N[(CH2)2N=CH-R-CH=N-(CH2)2]3N (R = m-C6H2OH-2-Me-5). In the synthesis the choice of counter ion and solvent prove crucial in controlling the Ln-Ln*composition. Choosing the optimal solvent and counter ion affords pure heterodinuclear complexes with any given combination of Gd(III)-Lu(III) including Y(III). To demon-strate the versatility of the synthesis all dinuclear combinations of Y(III), Gd(III), Yb(III) and Lu(III) were synthesized resulting in 10 novel complexes of the form LnLn*L(OTf)3 with LnLn* = YbGd 1, YbY 2, YbLu 3, YbYb 4, LuGd 5, LuY 6, LuLu 7, YGd 8, YY 9 and GdGd 10. Through the use of 1H, 13C NMR and mass spectrometry the heterodinuclear nature of YbGd, YbY, YbLu, LuGd, LuY and YGd was confirmed. Crystal structures of LnLn*L(NO3)3 reveal short Ln-Ln distances of ~3.5 Å. Using SQUID magnetometry the exchange coupling between the lanthanide ions was found to be anti-ferromagnetic for GdGd and YbYb while ferromagnetic for YbGd

Analysis of vibronic coupling in a 4f molecular magnet with FIRMS

Vibronic coupling, the interaction between molecular vibrations and electronic states, is a pervasive effect that profoundly affects chemical processes. In the case of molecular magnetic materials, vibronic, or spin-phonon, coupling leads to magnetic relaxation, which equates to loss of magnetic memory and loss of phase coherence in molecular magnets and qubits, respectively. The study of vibronic coupling is challenging, and most experimental evidence is indirect. Here we employ far-infrared magnetospectroscopy to probe vibronic transitions in in [Yb(trensal)] (where H3trensal = 2,2,2-tris(salicylideneimino)trimethylamine). We find intense signals near electronic states, which we show arise due to an “envelope effect” in the vibronic coupling Hamiltonian, and we calculate the vibronic coupling fully ab initio to simulate the spectra. We subsequently show that vibronic coupling is strongest for vibrational modes that simultaneously distort the first coordination sphere and break the C3 symmetry of the molecule. With this knowledge, vibrational modes could be identified and engineered to shift their energy towards or away from particular electronic states to alter their impact. Hence, these findings provide new insights towards developing general guidelines for the control of vibronic coupling in molecules.</p

Analysis of vibronic coupling in a 4f molecular magnet with FIRMS

OpenMOLCAS and Gaussian output files, FIRMS data (simulated and experimental), and luminescence data.For details of the methodology, see the "Methods" section of the associated paper

Analysis of vibronic coupling in a 4f molecular magnet with FIRMS

OpenMOLCAS and Gaussian output files, FIRMS data (simulated and experimental), and luminescence data

Outcomes of patients with systemic sclerosis treated with rituximab in contemporary practice: a prospective cohort study.

Objective To assess the safety and efficacy of rituximab in systemic sclerosis (SSc) in clinical practice. Methods We performed a prospective study including patients with SSc from the European Scleroderma Trials and Research (EUSTAR) network treated with rituximab and matched with untreated patients with SSc. The main outcomes measures were adverse events, skin fibrosis improvement, lung fibrosis worsening and steroids use among propensity score-matched patients treated or not with rituximab. Results 254 patients were treated with rituximab, in 58% for lung and in 32% for skin involvement. After a median follow-up of 2 years, about 70% of the patients had no side effect. Comparison of treated patients with 9575 propensity-score matched patients showed that patients treated with rituximab were more likely to have skin fibrosis improvement (22.7 vs 14.03 events per 100 person-years; OR: 2.79 [1.47-5.32]; p=0.002). Treated patients did not have significantly different rates of decrease in forced vital capacity (FVC)&gt;10% (OR: 1.03 [0.55-1.94]; p=0.93) nor in carbon monoxide diffusing capacity (DLCO) decrease. Patients having received rituximab were more prone to stop or decrease steroids (OR: 2.34 [1.56-3.53], p&lt;0.0001). Patients treated concomitantly with mycophenolate mofetil had a trend for better outcomes as compared with patients receiving rituximab alone (delta FVC: 5.22 [0.83-9.62]; p=0.019 as compared with controls vs 3 [0.66-5.35]; p=0.012). Conclusion Rituximab use was associated with a good safety profile in this large SSc-cohort. Significant change was observed on skin fibrosis, but not on lung. However, the limitation is the observational design. The potential stabilisation of lung fibrosis by rituximab has to be addressed by a randomised trial