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1.
Chem Commun (Camb) ; 2020 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-32728683

RESUMO

A series of water-soluble helicene dyes generating intense electrochemiluminescence (ECL) signal in physiological conditions is reported. Those species were prepared using diaza [4] and [6]helicenes as structural cores modified with sulfonate groups in various positions. Such groups improve their water solubility and can induce a red-shifted emission. Efficient ECL up to the near-infrared is achieved in water, demonstrating a viable strategy for the design of new near-infrared ECL dyes for bioassays and microscopy.

2.
Org Lett ; 2020 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-32559086

RESUMO

We report the development of two complementary methods for the Cu-catalyzed anti-Markovnikov borylation of one specific olefin in 2-substituted [n]dendralenes (n = 3-6). The first protocol operates with a bisphosphine ligand and occurs with high regio- and chemoselectivity for the terminal double bond, independently of the number of cross-conjugated alkenes. We show that the use of a chiral phosphanamine ligand enables the highly chemo-, regio-, and enantioselective borylation of the alkene cross-conjugated with the terminal olefin in [n]dendralenes.

3.
Inorg Chem ; 59(4): 2200-2208, 2020 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-32017539

RESUMO

Ligand protected copper nanoclusters with precise compositions have attracted considerable attention due to their unique photoluminescent properties. However, the acquisition of structural information, knowledge of the factors affecting the stability, and high quantum yields are prerequisites for assessing their applications in biomedicine as fluorescent contrast agents, biosensors, and probes for cells. Despite all the effort, only finite examples of single crystal structures of CuNCs are reported. Herein, we report the phosphine-free synthesis and structure determination of 2-PET protected CuNCs. The structure analysis established by single crystal X-ray diffraction reveals the formation of binary Cu74S15(2-PET)45 sulfide cluster. A similar phenomenon has been observed for several other chalcogenide-bridged copper clusters. The synthesized cluster possesses a rod-like structure, protected with 45 thiol ligands on the surface. Fifteen independent bridged-sulfur atoms couple to the copper atoms inside the core. Calculations for both a neutral and negatively charged cluster showed no major differences in their geometrical structures. Further analysis of frontier MO levels of the closed-shell anion predicts the HOMO-LUMO transition to be intramolecular L7 → L1 charge transfer, where "L7" and "L1" abbreviations refer to the corresponding sulfur layer in the structure. For the neutral cluster, the calculated spin density is delocalized over the two moieties. On the basis of TDDFT+TB calculations, the onset of the measured absorption spectrum could be satisfactorily reproduced.

4.
Inorg Chem ; 59(2): 1424-1435, 2020 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-31909978

RESUMO

The CrIIIN6 chromophores are particularly appealing for low-energy sensitization via energy transfer processes since they show extremely long excited state lifetimes reaching the millisecond range in the technologically crucial near-infrared domain. However, their properties were barely harnessed in multimetallic structures because of the lack of both monitoring methods and accessible synthetic pathways. We herein report a remedy to monitor and control the formation of CrIII-containing assemblies in solution via the design of a CrIIIN6 inert "complex-as-ligand" that can be included into polymetallic architectures. As a proof of concept, these CrN6 building blocks were reacted in solution with ZnII or FeII to give extended trinuclear linear Cr-M-Cr assemblies, the structure of which could be addressed by NMR spectroscopy despite the presence of two slowly relaxing CrIII paramagnetic centers. In addition to long CrIII excited state lifetimes and weak sensitivity to oxygen quenching, these polymetallic assemblies display controlled CrIII to MII energy transfers, which pave the way for use of the "complex-as-ligand" strategy for introducing photophysically active CrIII probes into light-converting polymetallic devices.

5.
Inorg Chem ; 59(1): 62-75, 2020 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-31117630

RESUMO

The binding of lanthanide containers [Ln(ß-diketonate)3dig] [dig = 1-methoxy-2-(2-methoxyethoxy)ethane] to aromatic tridentate N-donor ligands (L) in dichloromethane produces neutral nine-coordinate heteroleptic [LLn(ß-diketonate)3] complexes, the equilibrium reaction quotients of which vary with the total concentrations of the reacting partners. This problematic drift prevents the determination of both reliable thermodynamic stability constants and intrinsic host-guest affinities. The classical solution theory assigns this behavior to changes in the activity coefficients of the various partners in nonideal solutions, and a phenomenological approach attempts to quantitatively attribute this effect to some partition of the solvent molecules between bulk-innocent and contact-noninnocent contributors to the chemical potential. This assumption eventually predicts an empirical linear dependence of the equilibrium reaction quotient on the concentration of the formed [LLn(ß-diketonate)3] complexes, a trend experimentally supported in this contribution for various ligands L differing in lipophilicity and nuclearity and for lanthanide containers grafted with diverse ß-diketonate coligands. Even if the origin of the latter linear dependence is still the subject of debate, this work demonstrates that this approach can be exploited by experimentalists for extracting reliable thermodynamic constants suitable for analyzing and comparing host-guest affinities in organic solvents.

6.
J Am Chem Soc ; 142(1): 623-632, 2020 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-31825212

RESUMO

A Cu-catalyzed borylative carboxamidation reaction has been developed using vinylarenes and isocyanates. Alkynes, branched 1,3-dienes, and bicyclic alkenes were also found to be competent coupling partners. Using a chiral phosphanamine ligand, an enantioselective variant of this transformation was developed, affording a set of α-chiral amides with unprecedented levels of enantioselectivity. The synthetic utility of the method was demonstrated through a series of representative stereoretentive postcatalytic derivatizations.

7.
Inorg Chem ; 59(2): 1091-1103, 2020 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-31887022

RESUMO

The modulation of light emission by Fe(II) spin-crossover processes in multifunctional materials has recently attracted major interest for the indirect and noninvasive monitoring of magnetic information storage. In order to approach this goal at the molecular level, three segmental ligand strands, L4-L6, were reacted with stoichiometric mixtures of divalent d-block cations (M(II) = Fe(II) or Zn(II)) and trivalent lanthanides (Ln(III) = La(III) or Eu(III)) in acetonitrile to give C3-symmetrical dinuclear triple-stranded helical [LnM(Lk)3]5+ cations, which can be crystallized with noncoordinating counter-anions. The divalent metal M(II) is six-coordinate in the pseudo-octahedral sites produced by the facial wrapping of the three didentate binding units, the ligand field of which induces variable Fe(II) spin-state properties in [LnFe(L4)3]5+ (strictly high-spin), [LnFe(L5)3]5+ (spin-crossover (SCO) around room temperature), and [LnFe(L6)3]5+ (SCO at very low temperature). The introduction of the photophysically active Eu(III) probe in [EuFe(Lk)3]5+ results in europium-centered luminescence modulated by variable intramolecular Eu(III) → Fe(II) energy-transfer processes. The kinetic analysis implies Eu(III) → Fe(II) quenching efficiencies close to 100% for the low-spin configuration and greater than 95% for the high-spin state. Consequently, the sensitivity of indirect luminescence detection of Fe(II) spin crossover is limited by the resulting weak Eu(III)-centered emission intensities, but the dependence of the luminescence on the temperature unambiguously demonstrates the potential of indirect lanthanide-based spin-state monitoring at the molecular scale.

8.
Chem Sci ; 10(29): 7059-7067, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31588273

RESUMO

Oxygen atoms of cationic dioxa and azaoxa [6]helicenes can be exchanged by amino groups to form azaoxa and diaza [6]helicenes respectively. The mild reaction conditions developed herein allow the construction of libraries of derivatives with sensitive and/or functionalized side chains. Using enantioenriched dioxa or azaoxa helicene precursors, these exchanges lead to either near racemization (es 3%) or to a remarkable enantiospecificity (es up to 97%). This unusual behavior is fully characterized via experimental and computational mechanistic evidence. Based on these investigations, the enantiospecificity of the first transformation can be improved to 57-61%.

9.
J Am Chem Soc ; 141(33): 13244-13252, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31353904

RESUMO

The chiral resolution of a kinetically inert molecular ruby [Cr(dqp)2]3+ (1, dqp = 2,6-di(quinolin-8-yl)pyridine) displaying strong dual light emission at room temperature has been achieved. The wrapped arrangement of the six-membered dqp chelating ligands around the Cr(III) provided nonplanar helical conformations leading to the diastereoselective assembly of chiral bis-tridentate monometallic Cr(III)-helix. The PP-(+)-[Cr(dqp)2]3+ and MM-(-)-[Cr(dqp)2]3+ enantiomers could be separated and isolated by using cation-exchange chromatography and subsequent salt-metathesis with KPF6. X-ray crystallographic analysis based on Flack parameters assigned the absolute configurations of the two enantiomers. Circularly polarized luminescence (CPL) spectra showed two polarized emission bands within the NIR region corresponding to the characteristic metal-centered spin-flip Cr(2E → 4A2) and Cr(2T1 → 4A2) transitions with exceptionally high dissymmetry factors, |glum|, of 0.2 and 0.1, respectively, which are comparable to those reported for rare-earth chiral complexes. Photophysical properties also revealed an extremely long excited-state lifetime of 1.2 ms and a high quantum yield of 5.2% at room temperature in water. These properties make [Cr(dqp)2]3+ an ideal sensitizer for the preparation of enantiopure luminescent supramolecular energy-converting devices and also open up the possibility of using chiral Cr(III) chromophores for the construction of NIR-CPL materials and polarized photonic devices based on earth-abundant metals.

10.
Org Lett ; 21(3): 687-691, 2019 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-30657690

RESUMO

Selective formation of oxonium ylides from morpholines and α-diazo-ß-ketoesters was achieved. This was applied to the high-concentration (0.5 M) dirhodium-catalyzed (0.1 mol %) [3 + 6 + 3 + 6] synthesis of 18-membered ring diaza macrocycles (46%-72%). Late-stage functionalization of these derivatives is demonstrated. Mechanistic evidence for a novel (undesired) diazo decomposition pathway is also reported.

11.
Chem Commun (Camb) ; 54(94): 13228-13231, 2018 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-30406237

RESUMO

Substitution of Ru(ii)-based chromophores with cheaper Cr(iii)-based complexes in optically active metallo-supramolecular architectures is limited by the lack of synthetic strategies leading to heteroleptic Cr(iii)-polypyridyl complexes with long excited-state lifetimes. Herein, we report on a versatile method yielding heteroleptic bis(terdentate) Cr(iii) complexes with room temperature millisecond range excited-state lifetimes, tuneable electronic and photophysical properties and easy anchoring possibilities.

12.
Inorg Chem ; 57(22): 14362-14373, 2018 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-30376321

RESUMO

To exploit Cr(III) coordination complexes as sensitizers in supramolecular energy-converting devices, the latter optical relays should display long-lived excited states, broad emission bands, and tunable spatial and electronic connections to activator units. An ad-hoc versatile strategy has been therefore developed for the preparation of a family of luminescent pseudo-octahedral [CrN6] chromophores made up of ter-bidentate heteroleptic [Cr(phen)2(N-N'')]3+ complexes, where phen is 1,10-phenanthroline, and N-N' stands for α,α'-diimine ligands possessing peripheral substituents compatible with both electronic tuning and structure extensions. As long as the ligand field in these [CrN6] chromophores remains sufficiently strong to avoid back-intersystem crossing, photophysical studies indicate that the lifetime of the near-infrared emissive Cr(2E) excited state is poorly sensitive to ligand-based electronic effects. On the contrary, a drop in symmetry, the coupling with high frequency oscillators, and the implementation of sterical constraints in heteroleptic [Cr(phen)2(N-N')]3+ complexes affect both Cr(2E → 4A2) energies and Cr(2E) lifetimes. Altogether, [Cr(phen)2(phenAlkyn)]3+ (phenAlkyn = 5-ethynyl-1,10-phenanthroline) and [Cr(phen)2(dpma)]3+ (dpma = di(pyrid-2-yl)(methyl)amine) complexes mirror the favorable photophysical properties of homoleptic [Cr(phen)3]3+ and thus emerge as the best heteroleptic candidates for acting as sensitizers at room temperature, and below 100 K, respectively, in more complicated architectures.

13.
Chem Sci ; 9(35): 7043-7052, 2018 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-30310624

RESUMO

Straightforward synthesis and resolution of a series of chiral fluorescent macrocycles are presented, together with their electronic circular dichroism (ECD), strong excimer fluorescence (EF, λ 300 to 650 nm) and allied highly circularly polarized luminescence (CPL, g lum up to 1.7 × 10-2). The ECD, EF and CPL responses are strongly affected by the presence of metal ions (Na+, Ba2+) thanks to deep conformational changes. While ECD signals can be almost completely reversibly inverted upon the complexation/decomplexation of metal ions in a typical binary response, CPL signals are reversibly quenched concomitantly. The designed macrocycles display thus a remarkable combination of both +/- ECD and on/off CPL reversible switching.

14.
J Am Chem Soc ; 140(40): 12870-12876, 2018 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-30216056

RESUMO

The spin-crossover compound [Fe( n-Bu-im)3(tren)](PF6)2 shows an unusual long relaxation time of 20 h after light-induced excited spin state trapping when irradiating at 80 K. This is more than 40 times longer than when irradiating at 10 K. Optical absorption spectroscopy, magnetometry, and X-ray diffraction using synchrotron radiation were used to characterize and explain the different relaxation behaviors of this compound after irradiation below and above 70 K. Rearrangement of the butyl chains of the ligands occurring during the relaxation after irradiation above 70 K is thought to be responsible for the unusually long relaxation time at this temperature.

15.
Chemistry ; 24(63): 16873-16888, 2018 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-30171722

RESUMO

Chelate coordination of non-symmetrical didentate pyrazine-benzimidazole (L1) or pyridine-benzimidazole (L2) N-donor ligands around divalent iron in acetonitrile produces stable homoleptic triple-helical spin crossover [Fe(Lk)3 ]2+ complexes existing as mixtures of meridional (C1 -symmetry) and facial (C3 -symmetry) isomers in slow exchange on the NMR timescale. The speciation deviates from the expected statistical ratio mer/fac=3:1, a trend assigned to the thermodynamic trans-influence, combined with solvation effects. Consequently, the observed spin state FeII low-spin ↔FeII high-spin equilibria occurring in [Fe(Lk)3 ]2+ refer to mixtures of complexes in solution, an issue usually not considered in this field, but which limits rational structure-properties correlations. Taking advantage of the selective and quantitative formation of isostructural facial isomers in non-constrained related spin crossover d-f helicates (HHH)-[LnFe(Lk)3 ]5+ (Ln is a trivalent lanthanide, Lk=L5, L6), we propose a novel strategy for assigning pertinent thermodynamic driving forces to each spin crossover triple-helical isomer. The different enthalpic contributions to the spin state equilibrium found in mer-[Fe(Lk)3 ]2+ and fac-[Fe(Lk)3 ]2+ reflect the Fe-N bond strengths dictated by the trans-influence, whereas a concomitant solvent-based entropic contribution reinforces the latter effect and results in systematic shifts of the spin crossover transitions toward higher temperature in the facial isomers.

16.
J Am Chem Soc ; 140(34): 10820-10828, 2018 08 29.
Artigo em Inglês | MEDLINE | ID: mdl-30109926

RESUMO

We have designed a rigid photocleavable dianthracene-based ligand that reacts with ytterbium as coordination metal ion for the creation of a class of tridimensional light-degradable metal-organic framework (MOF). We demonstrated that we can obtain a high level of control on the disassembly of the MOF formed with this ligand which can be triggered either through light irradiation or temperature increase. The reversible 4π-4π photodimerization is the intrinsic chemical mechanism ruling the ligand and MOF cleavage. In the fields of biology and medicine, MOFs have sparked a strong interest as highly porous vehicles for drug release but have only been explored so far through the passive leakage of their payloads. The designed light-degradable MOFs can potentially overcome this limitation and serve as prototypes for drug delivery and corresponding therapeutic applications.

17.
Phys Chem Chem Phys ; 20(18): 12493-12502, 2018 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-29707721

RESUMO

The thermal spin transition of [Fe(pz)Pt(CN)4], pz = pyrazine, nanoparticles is compared with the one of the microcrystalline powder by magnetic susceptibility measurements, absorption spectroscopy and X-ray powder diffraction (XRPD) using synchrotron radiation. The thermal transition shows less cooperativity when decreasing the size due to the reduction of cluster formation. Surprisingly, the dispersion of the nanoparticles on a surface entails important effects on the spin crossover properties of the system. These effects are simulated and explained within the framework of the mechanoelastic model.

18.
Angew Chem Int Ed Engl ; 57(24): 7151-7155, 2018 06 11.
Artigo em Inglês | MEDLINE | ID: mdl-29673027

RESUMO

Polycyclic indoline-benzodiazepines can be accessed through the intermolecular reaction of Tröger bases with N-sulfonyl-1,2,3-triazoles. Under RhII catalysis, α-imino carbenes are generated and a subsequent cascade of [1,2]-Stevens, Friedel-Crafts, Grob, and aminal formation reactions yield the polycyclic heterocycles as single isomers (d.r.>49:1, four stereocenters including two bridgehead N atoms). Further ring expansion by insertion of a second α-imino carbene leads to elaborated polycyclic 9-membered-ring triazonanes.


Assuntos
Benzodiazepinas/síntese química , Indóis/síntese química , Compostos Policíclicos/síntese química , Benzodiazepinas/química , Catálise , Iminas/química , Indóis/química , Metano/análogos & derivados , Metano/química , Modelos Moleculares , Compostos Policíclicos/química , Ródio/química , Estereoisomerismo , Triazóis/química
19.
Chem Sci ; 9(2): 325-335, 2018 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-29629101

RESUMO

Metal-containing (bio)organic polymers are materials of continuously increasing importance for applications in energy storage and conversion, drug delivery, shape-memory items, supported catalysts, organic conductors and smart photonic devices. The embodiment of luminescent components provides a revolution in lighting and signaling with the ever-increasing development of polymeric light-emitting devices. Despite the unique properties expected from the introduction of optically and magnetically active lanthanides into organic polymers, the deficient control of the metal loading currently limits their design to empirical and poorly reproducible materials. We show here that the synthetic efforts required for producing soluble multi-site host systems Lk are largely overcome by the virtue of reversible thermodynamics for mastering the metal loading with the help of only two parameters: (1) the affinity of the luminescent lanthanide container for a single binding site and (2) the cooperative effect which modulates the successive fixation of metallic units to adjacent sites. When unsymmetrical perfluorobenzene-trifluoroacetylacetonate co-ligands (pbta-) are selected for balancing the charge of the trivalent lanthanide cations, Ln3+, in six-coordinate [Ln(pbta)3] containers, the explored anti-cooperative complexation processes induce nearest-neighbor intermetallic interactions twice as large as thermal energy at room temperature (RT = 2.5 kJ mol-1). These values have no precedent when using standard symmetrical containers and they pave the way for programming metal alternation in luminescent lanthanidopolymers.

20.
Chemistry ; 2018 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-29698563

RESUMO

A series of nine C-functionalized cationic diazaoxatriangulene (DAOTA) dyes have been successfully synthesized and fully characterized, including X-ray structural analysis of four derivatives. The introduction of electron-withdrawing or -donating functions enables the tuning of both electro- and photochemical properties with, for instance, two consecutive (reversible) reductions or oxidations observed for nitro or amino derivatives, respectively. The substituents also impacted on the optical properties, with absorption maxima varying from λ=528 to 640 nm and fluorescence being shifted from the yellow to the red range, up to λ=656 nm.

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