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1.
Cureus ; 16(1): e53067, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38410314

RESUMO

Objective To report the outcomes with high-dose-rate (HDR) brachytherapy (BT) treatment in patients with lower eyelid basal cell carcinoma (BCC) and to evaluate the relationship between dosimetric parameters and acute and late toxicities. Material and methods A retrospective unicentric study with patients diagnosed with lower eyelid biopsy-proven BCC treated with HDR BT between January 2012 and December 2019. The prescribed dose was 36 Gy to 40 Gy in 9 to 10 fractions, twice daily, over five days. The primary endpoint was local control, and the secondary endpoints were acute and late toxicities, registered according to CTCAE v4.0. The cosmetic result was evaluated on a qualitative scale (the CAIB scale). Local control was calculated according to the Kaplan-Meier test. Two sample T-tests and a Wilcoxon signed-rank test were used to determine the association between dosimetric parameters and side effects. Results Fifty-eight patients with a median age of 76 years were included. Among these patients, 55.2% received adjuvant HDR BT and 44.8% received radical HDR BT. At a median follow-up of 44 months, there were four local relapses, achieving a probability of local control at four years of 95% and 100% in the adjuvant and radical groups, respectively. Acute toxicity occurred in 76% of patients with only one grade 3 event (radiation dermatitis). Late toxicity was present in 56%. Eight patients underwent treatment for grade 3 cataracts during follow-up. Cosmetic results were excellent or very good in 93% of patients. Acute conjunctival hyperemia is strongly associated with the dose received by the ocular globe (volumes of 0.1cc, 1cc, and 2 cc) (p<0.05). Conclusion Lower eyelid BCC treatment with interstitial HDR BT is associated with excellent local control, acceptable long-term side effects, and good cosmetic results.

2.
Angew Chem Int Ed Engl ; 63(4): e202316696, 2024 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-38051776

RESUMO

The development of chiral compounds with enhanced chiroptical properties is an important challenge to improve device applications. To that end, an optimization of the electric and magnetic dipole transition moments of the molecule is necessary. Nevertheless, the relationship between chemical structure and such quantum mechanical properties is not always clear. That is the case of magnetic dipole transition moment (m) for which no general trends for its optimization have been suggested. In this work we propose a general rationalization for improving the magnitude of m in different families of chiral compounds. Performing a clustering analysis of hundreds of transitions, we have been able to identify a single group in which |m| value is maximized along the helix axis. More interestingly, we have found an accurate linear relationship (up to R2 =0.994) between the maximum value of this parameter and the area of the inner cavity of the helix, thus resembling classical behavior of solenoids. This research provides a tool for the rationalized synthesis of compounds with improved chiroptical responses.

3.
Inorg Chem ; 62(49): 20030-20041, 2023 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-37991724

RESUMO

A new linear trinuclear Co(II)3 complex with a formula of [{Co(µ-L)}2Co] has been prepared by self-assembly of Co(II) ions and the N3O3-tripodal Schiff base ligand H3L, which is obtained from the condensation of 1,1,1-tris(aminomethyl)ethane and salicylaldehyde. Single X-ray diffraction shows that this compound is centrosymmetric with triple-phenolate bridging groups connecting neighboring Co(II) ions, leading to a paddle-wheel-like structure with a pseudo-C3 axis lying in the Co-Co-Co direction. The Co(II) ions at both ends of the Co(II)3 molecule exhibit distorted trigonal prismatic CoN3O3 geometry, whereas the Co(II) at the middle presents an elongated trigonal antiprismatic CoO6 geometry. The combined analysis of the magnetic data and theoretical calculations reveal strong easy-axis magnetic anisotropy for both types of Co(II) ions (|D| values higher than 115 cm-1) with the local anisotropic axes lying on the pseudo-C3 axis of the molecule. The magnetic exchange interaction between the middle and ends Co(II) ions, extracted by using either a Hamiltonian accounting for the isotropic magnetic coupling and ZFS or the Lines' model, was found to be medium to strong and antiferromagnetic in nature, whereas the interaction between the external Co(II) ions is weak antiferromagnetic. Interestingly, the compound exhibits slow relaxation of magnetization and open hysteresis at zero field and therefore SMM behavior. The significant magnetic exchange coupling found for [{Co(µ-L)}2Co] is mainly responsible for the quenching of QTM, which combined with the easy-axis local anisotropy of the CoII ions and the collinearity of their local anisotropy axes with the pseudo-C3 axis favors the observation of SMM behavior at zero field.

4.
Dalton Trans ; 52(21): 7225-7238, 2023 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-37166056

RESUMO

Two new complexes [FeIII(Tp)(CN)2(µ-CN)MnIICl(HL1)]·3DMF (1) and {[FeIII(Tp)(CN)(µ2-NC)2CuII(HL2)](ClO4)}2·6DMF (2) (HL1 = 2-((((1-methylbenzimidazol-2-yl)methyl)(pyridin-2-ylmethyl)amino)methyl)phenol and HL2 = 2-(((pyridin-2-ylmethyl)(quinolin-2-ylmethyl)-amino)methyl)phenol) have been synthesized and characterized by elemental analysis and IR and UV/vis spectroscopy. Structural analysis revealed that 1 is a discrete dinuclear coordination complex and 2 is a discrete tetranuclear coordination complex. In complex 1, each MnII is in a distorted octahedral MN4OCl environment where coordination is satisfied by three nitrogen atoms and one oxygen atom of the ligand, and a chloride group and one nitrogen atom from cyanide. In complex 2, each Cu is in a distorted octahedral MN5O environment where coordination is satisfied by three nitrogen atoms and one oxygen atom of the ligand, and two nitrogen atoms from two cyanides. Direct current (dc) variable-temperature magnetic susceptibility measurements on polycrystalline samples of 1 and 2 were carried out in the temperature range of 1.8-300 K. Investigation of the magnetic properties reveals the occurrence of weak antiferromagnetic coupling between the low-spin FeIII (S = 1/2) ions and high-spin MnII (S = 5/2) ions in 1, while 2 exhibits ferro- and antiferromagnetic coupling between the metal ions in the tetranuclear CuII2FeIII2 unit. DFT calculations show ferromagnetic coupling in both complexes, although this appears to be weak in the case of complex 1. In addition, magnetostructural correlations reveal the magnetic behavior against Mn-N-C and Fe-C-N angles in 1 and Cu-N-C and Fe-C-N angles in 2.

5.
Mol Biol Evol ; 40(3)2023 03 04.
Artigo em Inglês | MEDLINE | ID: mdl-36788592

RESUMO

Many metabolites are generated in one step of a biochemical pathway and consumed in a subsequent step. Such metabolic intermediates are often reactive molecules which, if allowed to freely diffuse in the intracellular milieu, could lead to undesirable side reactions and even become toxic to the cell. Therefore, metabolic intermediates are often protected as protein-bound species and directly transferred between enzyme active sites in multi-functional enzymes, multi-enzyme complexes, and metabolons. Sequestration of reactive metabolic intermediates thus contributes to metabolic efficiency. It is not known, however, whether this evolutionary adaptation can be relaxed in response to challenges to organismal survival. Here, we report evolutionary repair experiments on Escherichia coli cells in which an enzyme crucial for the biosynthesis of proline has been deleted. The deletion makes cells unable to grow in a culture medium lacking proline. Remarkably, however, cell growth is efficiently restored by many single mutations (12 at least) in the gene of glutamine synthetase. The mutations cause the leakage to the intracellular milieu of a highly reactive phosphorylated intermediate common to the biosynthetic pathways of glutamine and proline. This intermediate is generally assumed to exist only as a protein-bound species. Nevertheless, its diffusion upon mutation-induced leakage enables a new route to proline biosynthesis. Our results support that leakage of sequestered metabolic intermediates can readily occur and contribute to organismal adaptation in some scenarios. Enhanced availability of reactive molecules may enable the generation of new biochemical pathways and the potential of mutation-induced leakage in metabolic engineering is noted.


Assuntos
Evolução Biológica , Vias Biossintéticas , Sobrevivência Celular , Mutação , Prolina
6.
Dalton Trans ; 51(34): 12954-12967, 2022 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-35960153

RESUMO

A family of Mn(II)Ln(III) dinuclear and tetranuclear complexes (Ln = Gd and Dy) has been prepared from the compartmental ligands N,N'-dimethyl-N,N'-bis(2-hydroxy-3-formyl-5-bromobenzyl)ethylenediamine (H2L1) and N,N',N''-trimethyl-N,N''-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H2L2). The Mn(II)Gd(III) complexes exhibit antiferromagnetic interactions between Mn(II) and Gd(III) ions in most cases, which are supported by Density Functional Theory (DFT) calculations. Experimental magneto-structural correlations carried out for the reported complexes and other related complexes found in bibliography show that the highest ferromagnetic coupling constants are observed in di-µ-phenoxido bridged complexes, which is due to the planarity of the Mn-(µ-O)2-Gd bridging fragment and to the high Mn-O-Gd angles. The effect of these angles has been studied by DFT calculations performed on a di-µ-phenoxido doubly bridged model. The magneto-thermal properties of the Mn(II)Gd(III) based complexes have also been measured, concluding that the magnitude of the Magneto-Caloric Effect (MCE) is due to the strength rather than to the nature of the magnetic coupling. Moreover, when two Mn(II)Gd(III) dinuclear units are connected by two carbonato-bridging ligands the MCE is enhanced, obtaining a maximum magnetic entropy change of 36.4 Jkg-1 K-1 at ΔB = 7 T and T = 2.2 K. On the other hand, one of the dinuclear Mn(II)Dy(III) complexes displays Single-Molecule Magnet (SMM) behaviour with an energy barrier of 14.8 K under an applied external field of 1000 Oe.

7.
Cureus ; 14(3): e22842, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-35399459

RESUMO

AIM: To assess the tendencies of radiation oncologists (ROs) in adjusting radiotherapy treatments (RTH) according to the coronavirus disease 2019 (COVID-19) status of patients during the early severe acute respiratory syndrome coronavirus 2 (SARS-COV2) pandemic in Europe. MATERIAL AND METHODS: An electronic survey was sent to 79 academic RTH departments across Europe. Only one respondent per institution was included. Respondents were asked how they would adjust RTH treatments based on COVID-19 status for more common cancers during the first wave of the pandemic. Respondents were also asked to report the number of external beam radiotherapy (EBRT) units and the number of new cases referred to their department. Descriptive statistical analysis was conducted focusing on different cancers. RESULTS: The overall response rate to the survey was 30.38% (24 institutions from 13 European countries). There was a wide range of different institutions regarding the number of patients, radiation oncologists, and facilities. A large proportion of respondents supported adjustment of RTH treatment (delay or switch to a shorter fractionation) for COVID-19-negative patients during the first wave of the pandemic only for early breast cancer (20% delay, 42.3% shorter), prostate cancer (53.6% delay, 21.4% shorter), and benign brain tumours (32% delay, 12% shorter). For COVID-19-negative patients with other cancers, most respondents recommended the standard RTH treatment. For COVID-19-positive patients, most respondents favoured a delay in RTH treatment or a shorter fractionation, regardless of cancer type and stage. CONCLUSION: The patient's COVID status significantly influenced the decision to undergo RTH treatment, regardless of the type and aggressiveness of cancer.

8.
Case Rep Oncol ; 14(1): 184-189, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33776701

RESUMO

A 67-year-old previously healthy woman presented with progressive visual impairment including bitemporal hemianopsia. A brain magnetic resonance imaging revealed a contrast-enhancing mass in the optic chiasm, spreading along the left optic tract. The patient underwent a transcranial biopsy of the left optical tract that yielded a diagnosis of diffuse large B-cell lymphoma. CT scans of the chest, abdomen, and pelvis, PET-CT, and bone marrow biopsy revealed no evidence of systemic lymphoma. Thus, the final diagnosis was of primary central nervous system lymphoma of the optic chiasm. Systemic treatment was initiated with full response. Six months after the end of the treatment, recurrence at cerebellum parenchyma and left tentorium was recorded. A new systemic treatment achieved full response. A second recurrence was noted in an optical coherence tomography of the right eye, 2 years after the initial diagnosis. The patient was treated with intravitreal methotrexate with initial success, but eventual failure after 10 months. Intravitreal rituximab was used with no effect. The patient was then referred to radiotherapy and underwent external beam radiotherapy with VMAT. There were no acute toxicities to report. After the radiotherapy treatment, at 1-year follow-up, the patient has no evidence of disease. Long-term toxicities were recorded and are considered manageable. The present case emphasizes the role of ocular irradiation as an option in the management of intraocular lymphoma patients, including in the salvage setting, with an acceptable ocular toxicity profile.

9.
Rep Pract Oncol Radiother ; 25(6): 860-866, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32982591

RESUMO

AIM: The aim of this study was to compare the outcomes, patterns of failure and laryngeal preservation rates in patients with T1N0 glottic cancer treated with surgery or radiotherapy. MATERIALS/METHODS: Retrospective study of T1N0 glottic cancer patients treated in our institution between January 2007 and December 2017. Histologically proven squamous cell carcinoma patients, treated with upfront cordectomy/partial laryngectomy (S group) or radiotherapy (RT group) were included. Elective treatment of the neck was not permitted. Local failure (LF), disease-free survival (DFS), ultimate disease-free survival (UDFS), laryngectomy-free survival (LFS), disease-specific mortality (DSM) and overall survival (OS) were evaluated. RESULTS: Two hundred and one patients were eligible (172 S group, 29 RT group), with a median follow-up of 38.8 months. Overall, 33 (16%) patients had a recurrence, 30 (17%) in the S group and 3 (10%) in the RT group. Local failure was the predominant site of failure (28 S, 2 RT). Overall, of all those that were salvaged, 17 (8%) underwent total laryngectomy (15 S, 2 RT). There was no significant difference in the 5-year cumulative incidence of LF (20.8% S, 8.1% RT, p = 0.138), 5-y LFS (85.0% vs. 91.7%, p = 0.809), 5-y DFS (67.5% vs. 82.1%, p = 0.343), 5-y UDFS (82.5% vs. 90.3%, p = 0.647) and 5-y OS (84.5% vs. 90.3%, p = 0.892). Multivariate analysis showed no correlation between initial treatment and the analyzed outcomes. CONCLUSION: Primary surgery or radiotherapy were similar first line options, since they do not differ in all outcomes. Patients' and physician's preferences must be considered when choosing first treatment.

10.
Chem Commun (Camb) ; 56(66): 9473-9476, 2020 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-32812539

RESUMO

Herein, we present, for the first time, a 2D-MOF based on copper and 4-hydroxypyrimidine-5-carbonitrile as the linker. Each MOF layer is perfectly flat and neutral, as is the case for graphene. High pressure X-ray diffraction measurements reveal that this layered structure can be modulated between 3.01 to 2.78 Å interlayer separation, with an evident piezochromism and varying conductive properties. An analysis of the band structure indicates that this material is conductive along different directions depending on the application of pressure or H doping. These results pave the way for the development of novel layered materials with tunable and efficient properties for pressure-based sensors.

11.
Psychiatr Danub ; 32(2): 210-213, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32796786

RESUMO

The auditory N1 component has been gaining interest as a possible biomarker in schizophrenia (SCZ). N1 to right (RE) and left ear (LE) amplitudes and latencies were assessed using a monoaural auditory oddball paradigm in 12 SCZ subjects and 15 matched healthy controls (M=40.1±8.53 and 39.4±7.73, respectively). T-student test revealed no differences between RE and LE stimulation for N1 amplitude and latency to both groups. However, there were differences in peak-to-peak N1 amplitudes between the two groups for both LE (t=-3.067; ρ=0.003) and RE (t=-2.794; ρ=0.007). These findings strengthen auditory N1 has an electrophysiological biomarker for schizophrenia.


Assuntos
Potenciais Evocados Auditivos , Esquizofrenia , Biomarcadores , Eletroencefalografia , Humanos , Tempo de Reação , Esquizofrenia/diagnóstico
12.
Rep Pract Oncol Radiother ; 25(4): 521-526, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32477017

RESUMO

PURPOSE: Report our matured outcomes of European nasopharyngeal carcinoma (NPC) treatment from a non-endemic region in the IMRT era. METHODS: We reviewed 109 consecutive patients with biopsy proven NPC treated between 2009 and 2013. All received IMRT as per RTOG 0615. Toxicity was scored accordingly to CTCAE 4.03. Platinum-based chemotherapy was delivered following the Intergroup 0099. RESULTS: Median age of 53 years; 97% Caucasian; 74% male; 72% WHO grade III; 43% T1; 14% T2; 18% T3, 25% T4; 17% N0; 17% N1; 39% N2; 27% N3. Compliance to adjuvant chemotherapy was 88%. With a median follow up of 56 months, the 4-year local control was 90.2% (88.6% for T1; 100% for T2; 85% for T3; and 91.7% for T4), the 4-year distant metastases-free survival was 86% and an overall survival rate was 77%. Local control and survival were better in G3 (p < 0.001 and p = 0.032, respectively). Xerostomia was the most frequent late toxicity in 55% (n = 60). Hypothyroidism requiring hormonal reposition occurred in 15.5% (n = 17). From the 36 deaths, 20 were due to distant metastases, 3 grade 5 toxicity, 2 from local progression, 5 non-cancer deaths and unknown cause in the remaining 6. On multivariable analysis, age (p = 0.017), local recurrence and distant metastases were associated with death (p < 0.001, both). CONCLUSION: Our matured data from the IMRT era showed a major improvement from our 3D cohort series reaching excellent local and regional control, even in T4. Local recurrences, despite few, and distant metastases were correlated with the risk of death.

14.
Org Biomol Chem ; 17(36): 8425-8434, 2019 09 28.
Artigo em Inglês | MEDLINE | ID: mdl-31469142

RESUMO

In this work we describe the ability of a simple enantiopure sulfoxide group to promote folding of oligo ortho-phenylene ethynylenes (o-OPEs) with one helical sense. A family of foldamers with up to seven triple bonds was synthesized and fully characterized. Moreover, changes in structure and chiroptical properties caused by Ag(i) coordination have been studied by NMR, UV, VCD and ECD measurements. Quantum mechanical DFT calculations support experimental results.

15.
Chem Commun (Camb) ; 55(72): 10685-10688, 2019 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-31432053

RESUMO

Intrinsically chiral double stapled ortho-oligo phenylene ethynylenes (o-OPEs) 1 show glum values up to 5.5 × 10-2, the second highest value ever observed for a simple organic molecule (SOM). DFT calculations of molecular spectra and properties encompassing electric and magnetic dipole transition moments account for these observations.

16.
Sci Total Environ ; 650(Pt 1): 1207-1215, 2019 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-30308808

RESUMO

In this study, a nickel organic xerogel (X-Ni) was used as semiconductor photocatalyst for the degradation of the herbicide diuron (DRN) in aqueous solution. The main objective of this work was to analyze and compare the effectiveness of solar irradiation to remove DRN from water both by direct photolysis and photocatalytic degradation. We examined the influence of the initial concentration of the herbicide, the solution pH, the presence of different ions in the medium, the chemical composition of the water, and the presence of a photocatalyst, after 240 min of irradiation. Direct photolysis achieved a low percentage of DRN degradation but was favored: i) by a reduction in the initial concentration of the herbicide (from 35.6% to 79.0% for 0.150 × 10-3 mol/L and 0.021 × 10-3 mol/L of DRN, respectively) and ii) at solution pHs at which diuron is positively charged (78.6% for pH 2 and 50.4% for pH 7), as suggested by DFT calculations carried out for DRN and its protonated form (DRN-H+). The corresponding mono-demethylated DRN derivative, 1-(3,4-dichlorophenyl)-3-methylurea (DCPU), was identified as a DRN degradation byproduct. In addition, the presence of certain anions in the medium significantly affected the overall degradation process by direct photolysis, due to the additional generation of HO radicals. We highlight that the presence of X-Ni considerably improved the photodegradation process under solar irradiation. The photocatalytic degradation rate constant was directly proportional to the xerogel concentration, because an increase in catalyst dose produced an increase in surface active sites for the photodegradation of DRN, enhancing the overall efficiency of the process. Thus, when 4167 mg/g of X-Ni was added, the DRN removal rate was 3-fold higher and both percentage of degradation and mineralization increased 88.5% with respect to the results obtained by direct photolysis.

17.
Chem Commun (Camb) ; 54(99): 13985-13988, 2018 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-30480686

RESUMO

Here we describe a new class of CPL switches based on oxophilic interactions between chiral sulfoxide-containing ortho-phenylene ethynylene (o-OPE) foldamers and cationic metals. These systems represent a unique case combining high glum values (up to 0.7 × 10-2) and high quantum yields in both folded ON and unfolded OFF CPL states.

18.
Inorg Chem ; 57(19): 12338-12346, 2018 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-30207469

RESUMO

We present here a novel example of spin crossover phenomenon on a Fe(II) one-dimensional chain with unusual N5S coordination sphere. The [{Fe(tpc-OMe)(NCS)(µ-NCS)} n] (1) compound was prepared using the tridentate tpc-OMe ligand (tpc-OMe = tris(2-pyridyl)methoxymethane), FeCl2·4H2O, and the KSCN salt. Crystallographic investigations revealed that the Fe(II) ions are connected by a single bridging NCS- ligand (µ-κN:κS-SCN coordination mode) to afford a zigzag neutral chain running along the [010] direction, in which the thiocyanato bridging groups adopt a cis head-to-tail configuration. The (N5S) metal environment arises from one thiocyanato-κS and two thiocyanato-κN ligands and from three pyridine of the fac-tpc-OMe tripodal ligand. This compound presents a unique extension of Fe(II) binuclear complexes into linear chains built on similar tripodal ligands and bridging thiocyanate anions. Compound 1 shows a spin crossover (SCO) behavior which has been evidenced by magnetic, calorimetric, and structural investigations, revealing a sharp cooperative spin transition with a transition temperature of ca. 199 K. Temperature scan rate studies revealed a very narrow hysteresis loop (∼1 K wide). Photoswitching of this compound was also performed, evidencing a very fast relaxation process at low temperature. Among other factors, the linearity of the N-bound terminal thiocyanato ligand appears as the main structural characteristic at the origin of the presence of the SCO transition in compound 1 and in the two others Fe(II) previous systems involving thiocyanato-bridges and tripodal tris(2-pyridyl)methane ligands.

19.
Inorg Chem ; 57(9): 5307-5319, 2018 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-29659263

RESUMO

Acyl(σ-norbornenyl)rhodium(III) dimer [Rh(µ-Cl)(C9H6NCO)(C7H9)L]2 (1) (C7H9 = σ-norbornenyl; L = 4-picoline, isoquinoline) reacts with diphenylphosphine oxide (SPO) to undergo a one-pot reaction involving (i) cleavage of the chloride bridges and coordination of the phosphine, (ii) C-C bond coupling between acyl and norbornenyl in a 18e species, and (iii) ligand-assisted outer-sphere O(P)-to-O(C) hydrogen transfer, to afford mononuclear 16e species [RhCl{(C9H6NC(O)C7H9)(Ph2PO)H}(L)] (2) containing a quinolinyl-(norbornenylhydroxyalkyl) fragment hydrogen-bonded to a κ1- P-phosphinite ligand. Pentacoordinated 2, which adopt a distorted trigonal bipyramidal structure, are kinetic reaction products that transform into the thermodynamic favored isomers 3. Structures 3 contain an unusual weak η1-C anagostic interaction involving the rhodium atom and one carbon atom of the olefinic C-H bond of the norbornenyl substituent in the chelating quinolinyl-hydroxyalkyl moiety. Their structure can be described as pseudoctahedral, through a 5 + 1 coordination, with the anagostic interaction in a trans disposition with respect to the phosphorus atom of the phosphinite ligand. Complexes were characterized in solution by NMR spectroscopy and electrospray ionization mass spectrometry. Complex [RhCl{(C9H6NC(O)C7H9)(Ph2PO)H}(4-picoline)] (3a) was also identified by X-ray diffraction. Density functional theory calculations confirm the proposed structures by a plausible set of mechanisms that accounts for the 1 (monomer) → 2 → 3 transformation. Lowest-energy pathways involve reductive elimination of quinolinylnorbornenylketone, still coordinated in the rhodium(I) species thus formed, followed by O-to-O hydrogen transfer from κ1- P-SPO to the sp3 hybridized carbonyl group (formal alkoxide) avoiding the otherwise expected classical release of ketone. Theoretical 13C NMR studies also confirm the experimental spectral data for the considered structures.

20.
Inorg Chem ; 57(7): 3683-3698, 2018 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-29565579

RESUMO

A family of MnIIILnIII strictly dinuclear complexes of general formula [MnIII(µ-L)(µ-OMe)(NO3)LnIII(NO3)2(MeOH)] (LnIII = Gd, Dy, Er, Ho) has been assembled in a one pot synthesis from a polydentate, multipocket aminobis(phenol)ligand [6,6'-{(2-(1-morpholyl)ethylazanediyl)bis(methylene)}bis(2-methoxy-4-methylphenol)], Mn(NO3)2·4H2O, Ln(NO3)3· nH2O, and NEt3 in MeOH. These compounds represent the first examples of fully structurally and magnetically characterized dinuclear MnIIILnIII complexes. Single X-ray diffraction studies reveal that all complexes are isostructural, consisting of neutral dinuclear molecules where the MnIII and LnIII metal ions, which exhibit distorted octahedral MnN2O4 and distorted LnO9 coordination spheres, are linked by phenoxide/methoxide double bridging groups. Static magnetic studies show that the MnIIIGdIII derivative exhibits a weak antiferromagnetic interaction between the metal ions, with a negative axial zero-field splitting D parameter. The MnIIIGdIII complex shows a notable magnetocaloric effect with magnetic entropy change at 5 T and 3 K of -Δ Sm = 16.8 J kg-1 K-1. Theoretical studies were performed to support the sign and magnitude of the magnetic anisotropy of the MnIII ion ( ab initio), to predict the value and nature of JMnGd, to disclose the mechanism of magnetic coupling, and to establish magneto-structural correlations (DFT calculations). The results of these calculations are corroborated by quantum theory of atoms in molecule analysis (QTAIM). Finally, MnIII-DyIII and MnIII-ErIII complexes show field-induced slow relaxation of the magnetization but without reaching a maximum above 2 K in the out-of-phase ac susceptibility. Ab initio calculations were also performed on MnIII-DyIII/HoIII systems to unravel the origin behind the weak SMM characteristics of the molecules possessing two strongly anisotropic ions. The mechanism of magnetic relaxation was developed, revealing a large QTM/tunnel splitting at the single-ion level. Furthermore, the anisotropy axes of the MnIII and LnIII ions were calculated to be noncollinear, leading to reduction of the overall anisotropy in the molecules. Hence, the herein reported complexes demonstrate that a combination of two anisotropic metal ions does not guarantee SMM behavior.

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