Electronic Structure of Metallophlorins: Lessons from Iridium and Gold Phlorin Derivatives.

Phlorins have long remained underexplored relative to their fully conjugated counterparts, such as porphyrins, hydroporphyrins, and corroles. Herein, we have attempted to bridge that knowledge gap with a scalar-relativistic density functional theory (DFT) study of unsubstituted iridium and gold phlorin derivatives and a multitechnique experimental study of iridium-bispyridine and gold complexes of 5,5-dimethyl-10,15,20-tris(pentafluorophenyl)phlorin. Theory and experiments concur that the phlorin derivatives exhibit substantially smaller HOMO-LUMO gaps, as reflected in a variety of observable properties. Thus, the experimentally studied Ir and Au complexes absorb strongly in the near-infrared (NIR), with absorption maxima at 806 and 770 nm, respectively. The two complexes are also weakly phosphorescent with emission maxima at 950 and 967 nm, respectively. They were also found to photosensitize singlet oxygen formation, with quantum yields of 40 and 28%, respectively. The near-infrared (NIR) absorption and emission are consonants with smaller electrochemical HOMO-LUMO gaps of ∼1.6 V, compared to values of ∼2.1 V, for electronically innocent porphyrins and corroles. Interestingly, both the first oxidation and reduction potentials of the Ir complex are some 600 mV shifted to more negative potentials relative to those of the Au complex, indicating an exceptionally electron-rich macrocycle in the case of the Ir complex.

Phosphonate-substituted porphyrins as efficient, cost-effective and reusable photocatalysts.

Recent advances in visible light photocatalysis represent a significant stride towards sustainable catalytic chemistry. However, its successful implementation in fine chemical production remains challenging and requires careful optimization of available photocatalysts. Our work aims to structurally modify bioinspired porphyrin catalysts, addressing issues related to their laborious synthesis and low solubility, with the goal of increasing their efficiency and developing reusable catalytic systems. We have demonstrated the catalytic potential of readily available meso-tetrakis[4-(diethoxyphosphoryl)phenyl]porphyrins (M(TPPP)). Novel metal (Pd(II), Co(II) and In(III)) complexes with this ligand were prepared in good yields. These chromophores were characterized in solution using spectroscopic (NMR, UV-vis, fluorescence) and electrochemical methods. The introduction of phosphonate groups on the phenyl substituents of meso-tetraphenylporphyrins (M(TPP)) improves solubility in polar organic solvents without significantly altering the photophysical properties and photostability of complexes. This structural modification also leads to easier reductions and harder oxidations of the macrocycle for all investigated complexes compared to the corresponding TPP derivatives. The free base porphyrin, zinc(II), palladium(II), and indium(III) complexes were studied as photocatalysts for oxidation of sulfides to sulfoxides using molecular oxygen as a terminal oxidant. Both dialkyl and alkyl aryl sulfides were quantitatively transformed into sulfoxides under blue LED irradiation in the acetonitrile-water mixture (10 : 1 v/v) with a low loading (0.005-0.05 mol%) of porphyrin photocatalysts, where H2(TPPP) and Pd(TPPP) were found to be the most efficient. The reaction mechanism was studied using photoluminescence and EPR spectroscopies. Then, to access reusable catalysts, water-soluble derivatives bearing phosphonic acid groups, H2(TPPP-A) and Pd(TPPP-A), were prepared in high yields. These compounds were characterized using spectroscopic methods. Single-crystal X-ray diffraction analysis of Pd(TPPP-A) reveals that the complex forms a 3D hydrogen-bonded organic framework (HOF) in the solid state. Both H2(TPPP-A) and Pd(TPPP-A) were found to catalyze the photooxidation of sulfides by molecular oxygen in the acetonitrile-water mixture (1 : 1 v/v), while only Pd(TPPP-A) resulted in selective production of sulfoxides. The complex Pd(TPPP-A) was easily recovered through extraction in the aqueous phase and successfully reused in five consecutive cycles of the sulfoxidation reaction.

Poly(vinyl chloride) Dechlorination Catalyzed by Zirconium.

Poly(vinyl chloride) undergoes dechlorination in the presence of triethylsilane (Et3SiH) and a catalytic amount of [Cp2Zr(NPh2)][CH3B(C6F5)3] (1 b) at 40-80 °C, with up to 91 % efficiency. Stoichiometric reactivity studies conducted on cyclohexyl chloride as a model suggest that 1 b dechlorinates PVC by initial chloride abstraction, followed by hydride transfer to the cationic PVC chain from Et3SiH. Consumer items such as pipe fitting, vinyl disc or electric cable insulation undergo either dechlorination or hydrosilylation of the carbonyl-containing copolymer (polyvinyl acetate) or plasticizer (phthalate).

P(III)-Chirogenic Phosphinite Building Blocks by Stereospecific N→O Phosphinyl Migration.

In the recent past, the chirality borne by a phosphorus center has aroused growing interest in many fields, and the development of new methodologies, notably using inexpensive reagents and simple experimental conditions, has become topical. An efficient stereoselective synthesis of P-chirogenic phosphinites useful as chiral phosphorus building blocks is herein described thanks to a new intramolecular phosphorus rearrangement based on P*(III)-phosphinyl N→O migration. This rearrangement was performed by heating at 50 °C aminophosphine-boranes, easily prepared from chiral amino alcohols, with DABCO in toluene overnight. Twenty-seven P-chirogenic phosphinites and borane complexes were thus prepared in yields up to 89%. The crude P*(III)-phosphinites were in situ used in stereoselective synthesis of P-chirogenic aminophosphine-phosphinites, phosphinothioates, sec- and tert-phosphine-oxides, and mono- and diphosphines in overall yields ranging from 28 to 89% and with e.e. up to 99%. Twenty-one X-ray structures of P-chirogenic compounds were established, allowing us to attribute undoubtedly their absolute configuration and the stereochemistry of the reactions. Finally, new ferrocenyl-bridged diphosphine ligands synthesized from P*(III)-chirogenic diphosphinites were tested in asymmetric metal-catalyzed reactions, providing enantioselectivities up to 95% e.e. in allylation of α-naphthylmethylamine at room temperature. To conclude, this rearrangement opens up an efficient new way for the stereoselective synthesis of numerous classes of P-chirogenic phosphorus compounds, notably bearing bulky substituents.

Al and Zn phenoxy-amidine complexes for lactide ROP catalysis.

We report the synthesis of a new generation of phenoxy-amidine ligands based on an aryloxy moiety possessing an ortho-N-linked trisubstituted amidine. The reaction of the phenol-amidine proligands with aluminum and zinc alkyls gave mono- or bis-ligated complexes depending on the metal/ligand ratio used. The solid-state structure of four proligands and thirteen Zn and Al complexes has been determined by X-Ray diffraction analysis. The mono-ligated complexes present an aryloxy-bridged dimeric structure, which is retained in solution in the case of Zn complexes but not with aluminum according to DOSY NMR experiments. Bis(ligated) Al and Zn complexes exhibit fluxional behaviour in solution attributed to coordination-decoordination of the amidine moiety and the rotation around the amidine C-NR'2 and C-Ar bonds. These complexes were tested for the ROP of rac-lactide in solution and under bulk conditions. In both cases, the most performant catalysts are Zn complexes featuring a phenoxy-amidine ligand with a pendant additional dimethylamino arm.

Bis(salicylamidine) Ligands (FAlen): A Variant of Salen with "à la Carte" Denticity.

Ethylene- and phenylene-bridged bis(salicylamidine) ligands have been readily prepared from ethylene or phenylenediamine and iminium chloride derivatives generated in situ from N,N-dialkylsalicylamides. The former, in its diprotonated form (FAlenH2), reacts with AlMe3 to afford a zwitterionic dimethyldiphenoxyaluminate complex with the FAlen ligand monoprotonated and in a bidentate κ2O,O' fashion. A phenylene-bridged proligand behaves differently, yielding a neutral methylaluminum complex bearing a κ3O,N,O'-coordinated FAlen ligand. From these complexes, methyl anion abstraction with B(C6F5)3 or a reaction with Schrock's alcohol leads to the corresponding aluminum cationic or alkoxy complexes in which a κ4O,N,N',O'-coordination mode of the FAlen ligand is observed. X-ray diffraction studies of the proligands and of the complexes show that the amidine functions feature a trans configuration when the N-amidine atom is not coordinated to the metal and conversely a cis configuration when it is. Density functional theory calculations show that trans-cis isomerization of the amidine functions occurs upon coordination with the metal ion with very low energy barriers. They also confirm the intuition that the denticity of the FAlen ligands in the complexes is directly related to the electron richness of the metal ion. At last, FAlen Al complexes are used as initiators for the controlled ring-opening polymerization of rac-lactide to afford poly(lactic acid) with slight isotactic bias.

Al(III) and Ga(III) Bisphenolate Azadipyrromethene-Based "N2O2" Complexes as Efficient NIR-Fluorophores.

Aza-boron-dipyrromethenes (Aza-BODIPYs) are an increasingly studied class of fluorophores. They can be seen as an azadipyrromethene ("aza-DIPY") ligand rigidified by a metalloid, a boron atom. Based on this idea, a series of complexes of group 13 metals (aluminum and gallium) have been synthesized and characterized. The impact of the metal and of the nature of the substituents of aza-DIPY core were investigated. The photophysical and electrochemical properties were determined, and an X-ray structure of an azaGaDIPY was obtained. These data reveal that azaGaDIPY and azaAlDIPY exhibit significant red-shifted fluorescence compared to their analogue aza-BODIPY. Their emission can go up to 800 nm for the maximum emission length and up to NIR-II for the emission tail. This, associated with their electrochemical stability (no metal release whether oxidized or reduced) makes them a promising class of fluorophores for optical medical imaging. Moreover, X-ray structure and molecular modeling studies have shown that this redshift seems to be more due to the geometry around the boron/metal than to the nature of the metal.

Crystal structure of the two-dimensional coordination polymer poly[di-µ-bromido-bis-(µ-tetra-hydro-thiophene)-dicopper(I)].

The polymeric title compound, [Cu2Br2(C4H8S)2] n , CP1, represents an example of a two-dimensional coordination polymer resulting from reaction of CuBr with tetra-hydro-thio-phene (THT) in MeCN solution. The two-dimensional layers consist of two different types of rhomboid-shaped dinuclear Cu(µ2-Br)2Cu secondary building units (SBUs); one with a quite loose Cu⋯Cu separation of 3.3348 (10) Šand a second one with a much closer inter-metallic contact of 2.9044 (9) Å. These SBUs are inter-connected through bridging THT ligands, in which the S atom acts as a four-electron donor bridging each Cu(µ2-Br)2Cu unit in a µ2-bonding mode. In the crystal, the layers are linked by very weak C-H⋯·Br hydrogen bonds with H⋯Br distances of 2.95 Å, thus giving rise to a three-dimensional supra-molecular network.

Real-Time Observation of "Soft" Magic-Size Clusters during Hydrolysis of the Model Metallodrug Bismuth Disalicylate.

Colloidal bismuth therapeutics have been used for hundreds of years, yet remain mysterious. Here we report an X-ray pair distribution function (PDF) study of the solvolysis of bismuth disalicylate, a model for the metallodrug bismuth subsalicylate (Pepto-Bismol). This reveals catalysis by traces of water, followed by multistep cluster growth. The ratio of the two major species, {Bi9O7} and {Bi38O44}, depends on exposure to air, time, and the solvent. The solution-phase cluster structures are of significantly higher symmetry in comparison to solid-state analogues, with reduced off-center Bi3+ displacements. This explains why such "magic-size" clusters can be both stable enough to crystallize and sufficiently labile for further growth.

Crystal structures of two polymorphs of tixocortol pivalate.

Two polymorphs, (I) and (II), of (S)-{2-[(8S,9S,10R,11S,13S,14S,17R)-11,17-dihy-droxy-10,13-dimethyl-3-oxo-2,6,7,8,9,11,12,14,15,16-deca-hydro-1H-cyclo-penta-[a]phenanthren-17-yl]-2-oxoeth-yl} 2,2-di-methyl-propane-thio-ate, C26H38O5S, have been identified. They are ortho-rhom-bic, non-centrosymmetric (P212121). The structures display layers of mol-ecules conected via O-H⋯O hydrogen bonds along the b-axis direction in polymorph (I) and along the c-axis direction in polymorph (II). The structure of (II) exhibits disorder of the main mol-ecule.

Development of a novel highly anti-proliferative family of gold complexes: Au(i)-phosphonium-phosphines.

A family of gold(i)-phosphonium-phosphine complexes was synthesized thanks to an efficient 5-step strategy, which involves a phospha-Fries rearrangement. It enables the facile variation of the phosphonium moiety. All the complexes along with a synthetic intermediate were fully characterized (a crystal structure was obtained for two of them). The antiproliferative properties of the six novel complexes were evaluated on three human cancer cell lines (A549, MDA-MB-231, and SW480) and compared to those of three benchmark anticancer drugs used in clinics (oxaliplatin, 5-fluorouracil, and paclitaxel) and to a phosphonium-free gold(i) complex [Au(PPh3)Br]. All the gold(i) complexes, containing a phosphonium, displayed strong anti-proliferative properties. They were more efficient than oxaliplatin and 5-fluorouracil, and one of the complexes was even more efficient than paclitaxel.

2-Azabutadiene complexes of rhenium(I): S,N-chelated species with photophysical properties heavily governed by the ligand hidden traits.

The reaction of [Re(CO)3(THF)(µ-Br)]2 or [Re(CO)5X] (X = Cl, Br, I) with the diaryl-2-azabutadienes [(RS)2C[double bond, length as m-dash]C(H)-N[double bond, length as m-dash]CAr2] containing two thioether arms at the 4,4-position forms the luminescent S,N-chelate complexes fac-[(OC)3ReX{(RS)2C[double bond, length as m-dash]C(H)-N[double bond, length as m-dash]CAr2}] (1a-h). The halide abstraction by silver triflate converts [(OC)3ReCl{(PhS)2C[double bond, length as m-dash]C(H)-N[double bond, length as m-dash]CPh2}] (1c) to [(OC)3Re(OS([double bond, length as m-dash]O)2CF3){(PhS)2C[double bond, length as m-dash]C(H)-N[double bond, length as m-dash]CPh2}] (1j) bearing a covalently bound triflate ligand. The cyclic voltammograms reveal reversible S^N ligand-centred reduction and irreversible oxidation waves for all complexes. The crystal structures of nine octahedral complexes have been determined along with that of (NaphtylS)2C[double bond, length as m-dash]C(H)-N[double bond, length as m-dash]CPh2 (L6). A rich system of weak non-covalent intermolecular secondary interactions through CHX(Cl, Br)Re, CHO, COπ(Ph), CHπCO, CHO and CHS contacts has been evidenced. The photophysical properties have been investigated by steady-state and time-resolved absorption (fs transient absorption, fs-TAS) and emission (ns-TCSPC and ps-Streak camera) spectroscopy in 2-MeTHF solution at 298 and 77 K. The emission bands are composed of either singlet (450 < λmax < 535 nm) and/or triplet emissions (at 77 K only, λmax < 640 nm, or appearing as a tail at λ > 600 nm), which decay in a multiexponential manner for the fluorescence (short ps (i.e.

Design of P-Chirogenic Aminophosphine-Phosphinite Ligands at Both Phosphorus Centers: Origin of Enantioselectivities in Pd-Catalyzed Allylic Reactions.

We have recently patented an unprecedented stereospecific N → O phosphinyl migration process which transforms P-chirogenic aminophosphines into phosphinites. A fine design of aminophosphine phosphinite ligands (AMPP*) derived from ephedrine and bearing a P-chirogenic center either at the aminophosphine or phosphinite moiety was performed. The synthesis of AMPP* ligands with a P-chirogenic aminophosphine moiety was based on the well-established stereospecific reaction of oxazaphospholidine borane with organolithium reagents, followed by trapping with a chlorophosphine and borane decomplexation. Concurrently, the preparation of AMPP* ligands with a P-chirogenic phosphinite moiety was performed by N → O phosphinyl migration of aminophosphines borane by heating at 50 °C with DABCO and then reaction with chlorophosphines. AMPP* ligands were studied in palladium-catalyzed asymmetric allylic alkylations, leading to enantioselectivities from 91% (R) to 95% ee (S). X-ray crystallographic data for relevant Pd-AMPP* complexes and computer modeling explained the origin of the enantioselectivities based on MO interactions of most stable conformers with nucleophiles.

Water-Soluble Aza-BODIPYs: Biocompatible Organic Dyes for High Contrast In Vivo NIR-II Imaging.

A simple NIR-II emitting water-soluble system has been developed and applied in vitro and in vivo. In vitro, the fluorophore quickly accumulated in 2D and 3D cell cultures and rapidly reached the tumor in rodents, showing high NIR-II contrast for up to 1 week. This very efficient probe possesses all the qualities necessary for translation to the clinic as well as for the development of NIR-II emitting materials.

A3- and A2B-fluorocorroles: synthesis, X-ray characterization and antiviral activity evaluation against human cytomegalovirus infection.

Twenty-nine fluorinated corroles were prepared, spectroscopically characterized, and studied for their antiviral activity against human cytomegalovirus infection. Six corroles were also fully characterized by X-ray crystallography giving insights on their geometrical features. The halogenated corroles reported herein exhibit significantly improved antiviral activity over their non-halogenated counterparts and over nitro-corrole analogs previously reported. Full activity of thirteen A3-corroles is achieved with four fluorine atoms present on the meso-phenyl ring reaching a selectivity index above 300. The maximum activity is achieved for A2B-corroles with selectivity indexes above 400. We thus demonstrate that the fluorocorrole is a highly potent platform to synthesize a new generation of anti hCMV molecules.

Synthesis, structure determination and characterization by UV-Vis and IR spectroscopy of bis-(diiso-propyl-ammonium) cis-di-chlorido-bis(oxalato-κ2 O 1,O 2)stannate(IV).

The organic-inorganic title salt, (C6H16N)2[Sn(C2O4)2Cl2] or ( i Pr2NH2)2[Sn(C2O4)2Cl2], was obtained by reacting bis-(diiso-propyl-ammonium) oxalate with tin(IV) chloride dihydrate in methanol. The SnIV atom is coordinated by two chelating oxalate ligands and two chloride ions in cis positions, giving rise to an [Sn(C2O4)2Cl2]2- anion (point group symmetry 2), with the SnIV atom in a slightly distorted octa-hedral coordination. The cohesion of the crystal structure is ensured by the formation of N-H⋯O hydrogen bonding between (iPr2NH2)+ cations and [SnCl2(C2O4)2]2- anions. This gives rise to an infinite chain structure extending parallel to [101]. The main inter-chain inter-actions are van der Waals forces. The electronic spectrum of the title compound displays only one high intensity band in the UV region assignable to ligand-metal ion charge-transfer (LMCT) transitions. An IR spectrum was also recorded and is discussed.

Diamondoid Nanostructures as sp3 -Carbon-Based Gas Sensors.

Diamondoids, sp3 -hybridized nanometer-sized diamond-like hydrocarbons (nanodiamonds), difunctionalized with hydroxy and primary phosphine oxide groups, enable the assembly of the first sp3 -C-based chemical sensors by vapor deposition. Both pristine nanodiamonds and palladium nanolayered composites can be used to detect toxic NO2 and NH3 gases. This carbon-based gas sensor technology allows reversible NO2 detection down to 50 ppb and NH3 detection at 25-100 ppm concentration with fast response and recovery processes at 100 °C. Reversible gas adsorption and detection is compatible with 50 % humidity conditions. Semiconducting p-type sensing properties are achieved from devices based on primary phosphine-diamantanol, in which high specific area (ca. 140 m2 g-1 ) and channel nanoporosity derive from H-bonding.

Ligand Noninnocence in Cobalt Dipyrrin-Bisphenols: Spectroscopic, Electrochemical, and Theoretical Insights Indicating an Emerging Analogy with Corroles.

Three cobalt dipyrrin-bisphenol (DPPCo) complexes with different meso-aryl groups (pentafluorophenyl, phenyl, and mesityl) were synthesized and characterized based on their electrochemistry and spectroscopic properties in nonaqueous media. Each DPPCo undergoes multiple oxidations and reductions with the potentials, reversibility, and number of processes depending on the specific solution conditions, the specific macrocyclic substituents, and the type and number of axially coordinated ligands on the central cobalt ion. Theoretical calculations of the compounds with different coordination numbers are given in the current study in order to elucidate the cobalt-ion oxidation state and the innocence or noninnocence of the macrocyclic ligand as a function of the changes in the solvent properties and degree of axial coordination. Electron paramagnetic resonance spectra of the compounds are obtained to experimentally assess the electron spin state. An X-ray structure of the six-coordinate complex is also presented. The investigated chemical properties of DPPCo compounds under different solution conditions are compared to those of cobalt corroles, where the macrocycle and metal ion also possess formal 3- and 3+ oxidation states in their air-stable forms.

Crystal structure of di-µ-hydroxido-bis-{aqua-[ethyl (1,10-phenanthrolin-3-yl)phospho-nato-κ2 N,N']copper(II)} hepta-hydrate.

In the title compound, [Cu2(OH)2{C12H7N2(PO3C2H5)}2(H2O)2]·7H2O, two Cu2+ cations are bridged by two hydroxide groups, forming a centrosymmetric binuclear complex. Each Cu2+cation is further coordinated by the N atoms of a bidentate ethyl (1,10-phenanthrolin-3-yl)phospho-nate anion and a water mol-ecule in a square-pyramidal geometry. In the crystal, a network of O-H⋯O hydrogen bonds involving the P(O)(O-)(OEt) groups, bridging hydroxyl groups, coordinated and uncoordinated water mol-ecules generates a three-dimensional supra-molecular structure. The ethyl group exhibits disorder and was modelled over three sites with occupancies of 0.455, 0.384 and 0.161.

Crystal structure of bis-(diiso-propyl-ammonium) molybdate.

The organic-inorganic title salt, (C6H16N)2[MoO4] or ( i Pr2NH2)2[MoO4], was obtained by reacting MoO3 with diiso-propyl-amine in a 1:2 molar ratio in water. The molybdate anion is located on a twofold rotation axis and exhibits a slightly distorted tetra-hedral configuration. In the crystal structure, the diiso-propyl-ammmonium ( i Pr2NH2)+ cations and [MoO4]2- anions are linked to each other through N-H⋯O hydrogen bonds, generating rings with R 12 12(36) motifs that give rise to the formation of a three-dimensional network. The structure was refined taking into account inversion twinning (ratio of ca 4:1 between the two domains).