Phosphine Oxide Ligands Research Articles

Chiral lanthanide lumino-glass for a circularly polarized light security device

Artificial light plays an essential role in information technologies such as optical telecommunications, data storage, security features, and the display of information. Here, we show a chiral lanthanide lumino-glass with extra-large circularly polarized luminescence (CPL) for advanced photonic security device applications. The chiral lanthanide glass is composed of a europium complex with the chiral (+)-3-(trifluoroacetyl)camphor ligand and the achiral glass promoter tris(2,6-dimethoxyphenyl)phosphine oxide ligand. The glass phase transition behavior of the Eu(III) complex is characterized using differential scanning calorimetry. The transparent amorphous glass shows CPL with extra-large dissymmetry factor of gCPL = 1.2. The brightness of the lumino-glass is one thousand times larger than that of Eu(III) luminophores embedded in polymer films of the same thickness at a Eu(III) concentration of 1 mM. The application of the chiral lanthanide lumino-glass in an advanced security paint is demonstrated.

Hot carriers perspective on the nature of traps in perovskites

Amongst the many spectacular properties of hybrid lead halide perovskites, their defect tolerance is regarded as the key enabler for a spectrum of high-performance optoelectronic devices that propel perovskites to prominence. However, the plateauing efficiency enhancement of perovskite devices calls into question the extent of this defect tolerance in perovskite systems; an opportunity for perovskite nanocrystals to fill. Through optical spectroscopy and phenomenological modeling based on the Marcus theory of charge transfer, we uncover the detrimental effect of hot carriers trapping in methylammonium lead iodide and bromide nanocrystals. Higher excess energies induce faster carrier trapping rates, ascribed to interactions with shallow traps and ligands, turning these into potent defects. Passivating these traps with the introduction of phosphine oxide ligands can help mitigate hot carrier trapping. Importantly, our findings extend beyond photovoltaics and are relevant for low threshold lasers, light-emitting devices and multi-exciton generation devices.

Enantioselective Twofold C−H Annulation of Formamides and Alkynes without Built‐in Chelating Groups

AbstractTwofold C−H annulation of readily available formamides and alkynes without built‐in chelating groups was achieved. Ni−Al bimetallic catalysis enabled by a bulky BINOL‐derived chiral secondary phosphine oxide (SPO) ligand proved to be critical for high reactivity and high selectivity. This reaction uses readily available formamides as starting materials and provides a concise synthetic pathway to a broad range of chiral ferrocenes in 40–98 % yield and 93–99 % ee.

Enantioselective Twofold C-H Annulation of Formamides and Alkynes without Built-in Chelating Groups.

Twofold C-H annulation of readily available formamides and alkynes without built-in chelating groups was achieved. Ni-Al bimetallic catalysis enabled by a bulky BINOL-derived chiral secondary phosphine oxide (SPO) ligand proved to be critical for high reactivity and high selectivity. This reaction uses readily available formamides as starting materials and provides a concise synthetic pathway to a broad range of chiral ferrocenes in 40-98 % yield and 93-99 % ee.

Insight into the influence of terminal ligands on magnetic exchange coupling in a series of dimeric copper(II) acetate adducts

AbstractA combination of experimental (SQUID magnetometry) and quantum‐chemical (BS‐DFT, CASSCF(n,m)/NEVPT2, DDCI3) methods is used to probe the influence of terminal ligands on magnetic exchange coupling in the series of [Cu2(μ2‐OAc)4L2] complexes with O‐donor terminal ligands extended by two novel complexes containing phosphine oxide ligands. The possibilities and limitations of these approaches are discussed. The influence of terminal ligands on magnetic superexchange interaction was quantified by two contributions—the first contribution is associated with structural changes within the {Cu(μ2‐OAc)4Cu} core, while the second contribution is due to the difference in the electronic influence of different terminal ligands at a given core geometry. Both contributions were found to be approximately of the same order of magnitude. These results indicate that magnetic exchange coupling, known to be highly sensitive to the distortions in core geometry, is not solely determined by the core structure. Our findings are consistent with the fact that various one‐ and multiparameter magnetostructural correlations reported in the literature have only a qualitative predictive capability.

A Rare Type of Rhenium(I) Diimine Complexes with Unsupported Coordinated Phosphine Oxide Ligands: Synthesis, Structural Characterization, Photophysical and Theoretical Study

This paper presents synthesis and photophysical investigation of a very rare type of the ReI diimine complexes, [Re(diimine)(CO)3(OPR3)]+, R = Ph, Cy; diimine – phenanthroline and neocuproine, containing monodentate (unsupported) phosphine oxide ligands. The obtained compounds have been structurally characterized in solid phase by using XRD crystallography, which revealed unusual distortions in the pseudo octahedral rhenium environment, which may be ascribed to intramolecular interligand (phosphine oxide – diimine) interaction rather than to crystal packing effect. Optimization of the ground state structure of these molecules with the DFT method also confirmed intramolecular origin of the observed structural peculiarities. The complexes display phosphorescence in solution and in solid state with the quantum yield up to 11 % and 14 %, respectively, which originates from 3MLCT excited state as demonstrated by DFT calculations. Comparative analysis of the ligand (L) effect onto emission energy in the [Re(neocuproine)(CO)3(L)] complexes (L = PPh3, NCMe, OPPh3, Cl–) showed that the position of emission wavelength in the corresponding complexes qualitatively correlates with cumulative donor ability of these ligands that is in complete agreement with the 3MLCT character of emission.

Polymerization of conjugated dienes and olefins promoted by cobalt complexes supported by phosphine oxide ligands

Four cobalt complexes supported by phosphine oxide (P=O) donors (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphine oxide) cobalt dichloride (Co1), (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphine oxide) cobalt bromide (Co2), N, N'-(pyridine-2,6-diyl)bis(P,P-di-tert-butylphosphinic amide) cobalt dichloride (Co3) and N, N'-(pyridine-2,6-diyl)bis(P,P-di-tert-butylphosphinic amide) cobalt dichloride (Co4) were prepared and characterized. Their catalyses performances in polymerization of isoprene, butadiene, myrcene as well as MMA and styrene were examined. In combination with AlEt2Cl, Co1 and Co2 are able to convert isoprene to polyisoprene, whereas the activities of Co3 and Co4 are much low. The resultant polyisoprene are mixture of cis-1,4 and 3,4 isomers, whose ratio are not significantly affected by the type of catalysts and polymerization conditions. Isoprene was found to be more active than myrcene, and butadiene in the case of Co1/AlEt2Cl, suggestive of compromised sterical and electronic effect from the alkyl group at 2-positon of monomers. The Co1/AlEt2Cl system is also moderately active in polymerizations of methyl methacrylate and styrene. Therefore, the current catalysts provided dual polymerization reactivities towards conjugated dienes and olefins that are rare in transition metals catalyzed coordinative polymerization.

Phosphine Oxide Ligand Based Tetrahedral CoII Complexes with Field-induced Slow Magnetic Relaxation Behavior Modified by Terminal Ligands.

Two isostructural mononuclear CoII complexes, [Co(xantpo)(NCE)2 ] (E=S (1) and O (2); xantpo=9,9-dimethyl-4,5-bis(diphenylphosphoryl) xanthene), supported by a bidentate phosphine oxide ligand are reported. The cobalt complexes exhibit characteristic tetrahedral structures coordinated with two oxygen and two nitrogen atoms. Magnetic property measurements show their similar static magnetic behaviours but very different dynamic magnetic behaviours. Both complexes show field-induced slow magnetic relaxation behaviours, but the relaxation of 2 is much slower than that of 1. Fittings to the magnetic data and ab initio CASSCF calculations reveal significant changes in the zero field splitting (ZFS) parameters (D and E), which can be attributed to the small geometrical changes of the Co ions and the different ligand field strength of the two terminal ligands.

A CF3-substituted diphosphine dioxide ligand that enhances both photoluminescence intensity and solubility of Eu(III) complexes

The author developed the di(3-trifluoromethylphenyl)[3-(dioctylphosphinyl)propyl]phosphine oxide (DPDO-mCF3) ligand in order to prepare Eu(III) complexes with high photoluminescence intensity and solubility. By coordinating the DPDO-mCF3 ligand to Eu(III), photoluminescence intensities were increased to 6.4 and 4.3 times those of tris(4,4,5,5,6,6,6-heptafluoro-1-(2-naphthyl)-1,3-hexanedionato)europium(III) (Eu(III)(hfnh)3; 4) and tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III) (Eu(III)(fod)3; 5), respectively. Coordination of the DPDO-mCF3 ligand also increased the asymmetry ratio, total photoluminescence quantum yield (ΦTOT), and absorbance of Eu(III) complexes. ΦTOT of Eu(III)(hfnh)3(DPDO-mCF3) (1) was 0.60 in ethyl acetate at a concentration of 1 × 10−3 mol/L and 0.82 in the solid state. In addition, ΦTOT of Eu(III)(fod)3(DPDO-mCF3) (2) is 0.39 in ethyl acetate at a concentration of 1 × 10−3 mol/L and 0.56 in the solid state. Solid-state quantum yields were larger than solution-state quantum yields across a wide wavelength region. Furthermore, the solubility of 2 in 2,3-dihydrodecafluoropentane (54 μmol/g) was far higher than that of 5 (7.2 μmol/g). DPDO-mCF3 is thus an innovative ligand for Eu(III) complexes, and Eu(III) complexes bearing a DPDO-mCF3 ligand are promising candidates for many applications, including LED devices, secure media, and sensing devices.

Variation of topologies and entanglements in metal-organic frameworks with mixed tris[4-(1H-imidazol-1-yl)phenyl]phosphine oxide and dicarboxylate ligands.

Six metal-organic frameworks with the combination of a novel tripodal ligand tris[4-(1H-imidazol-1-yl)phenyl]phosphine oxide (tipo) and different polycarboxylates, namely [Zn2(bpdc)2(tipo)(H2O)]·5H2O (1), [Cd(tipo)2][Cd2(bdc)3]·4H2O (2), [Cd2(ndc)2(tipo)2]·3H2O (3), [Cd2(bpedc)2(tipo)2]·15H2O (4), [Cd2(hfdc)2(tipo)2]·10H2O (5) and [Ni2(tipo)2(bpedc)(H2O)4]·2NO3·2DMF (6), were synthesized and structurally characterized. Compound 1 featured a 2D → 3D parallel polycatenation of a 3,3,4-connected net with an unusual 4 degrees of catenation and an index of separation of 2. Compound 2 showed an unprecedented polycatenation of charged networks 2D kgd and 3D pcu constructed by different organic ligands. Compound 3 exhibited a combination of a 2D → 3D parallel polycatenation of the sql net and polythreading. Compound 4 featured a 4-fold interpenetration of a 3,5-connected 3,5T1 net. Compound 5 displayed an unusual 2-fold interpenetration of the sdd net. Compound 6 presented a 2-fold interpenetration of the 3,4-connected bey net with a cationic framework. The luminescence properties of 1-5 in the solid state were investigated. Also, compound 6 showed a tendency for rapid selective dye capture and highly efficient Cr2O72- removal from aqueous solution.

Mercapto-benzothiazolyl based ruthenium(ii) borate complexes: synthesis and reactivity towards various phosphines.

The synthesis and reactivity of ruthenium complexes containing an anionic boron based ligand, supported by mercapto-benzothiazolyl heterocycles are presented. Specifically, the reaction of [(η6-p-cymene)Ru{P(OMe)2OR}Cl2], (1a: R = Me; 1b: R = H) with [H2B(mbz)2]- (mbz = 2-mercaptobenzothiazolyl) at room temperature afforded a series of borate complexes, namely [(L)Ru{κ3-H,S,S'-H2B(L)2}P(O)(OMe)(HL)], 2, [Ru{κ3-H,S,S'-H2B(L)2}2], 3 and [(κ2-N,S-L)P(OMe)3Ru{κ3-H,S,S'-H2B(L)2}], 4a; (L = C7H4NS2). The pivotal feature of 2 is the coordination of the Ru centre with a phosphorus atom of secondary phosphine oxide and mercapto-benzothiazolyl ligands. On the other hand, 3 features dual RuH-B interactions between Ru and B-H bonds of [H2B(mbz)2]-. Interestingly, along with 3, compound [(κ2-N,S-L)P(OPh)3Ru{κ3-H,S,S'-H2B(L)2}], 4b (L = C7H4NS2), was isolated upon treatment of the same borate with [(η6-p-cymene)RuCl2P(OPh)3], 1c, which is stabilized by δ-B-H interactions and one phosphite ligand. Furthermore, compound 3 promptly reacts with P(OR)3 to generate [(OR)3PRu-{κ2-S,S'-H2B(L)2}{κ3-H,S,S'-H2B(L)2}], (5a: R = Me, 5b: R = Ph; L = C7H4NS2) by breaking one of the RuH-B interactions. Upon heating, compound 5a converts into [(OMe)2OPRu{κ2-S,S'-HB(L)2}{κ3-H,S,S'-H2B(L)2}], 6a (L = C7H4NS2) by release of methane gas. Compound 6a is a unique example wherein the boron atom of the borate ligand is bound to an oxygen atom of the phosphite unit. In contrast, the thermolysis of 3 with PR2R' yielded [Ru{κ3-H,S,S'-H2B(L2)}(PR2R')2(L)], (7a: R = Me, R' = Ph; 7b: R = Ph; R' = Me; L = C7H4NS2), respectively, revealing the incorporation of two triphosphine ligands in the coordination sphere of ruthenium. Density functional theory (DFT) calculations were undertaken to provide an insight into the electronic structures of the complexes.

A first phosphine oxide-based extractant with high Am/Cm selectivity.

A new phosphine oxide ligand demonstrates high selectivity for the Am-Cm pair with SF = 2.9-3.5 and the Am-Eu pair with SF = 7.3-8.5 in a range of 0.1-3 M nitric acid. Thermodynamic measurements show that the entropy factor is responsible for selectivity observed in the extraction experiment. The most prevalent complexes of all three metal ions were (Ph2PyPO)2M(NO3)3. According to their DFT modelling, the M-N distances for the Cm ion were larger than those for Am, so the last ion enters deeper into the pseudo-cavity of the ligand, which causes the observed selectivity.

Neodymium dihalide complexes with a tridentate amidinate phosphine oxide ligand: synthesis, structure, and catalytic activity in isoprene polymerization

The deprotonation of amidine 2-[Ph2P(O)]C6H4NHC(But)=N(2,6-Me2C6H3) (1) with BunLi affords lithium amidinate {2-[Ph2P(O)]C6H4NLiC(But)=N(2,6-Me2C6H3)}2 (2) having a dimeric structure, as demonstrated by X-ray diffraction. New amidinate dihalide complexes {2-[Ph2P(O)]C6H4NC(But)N(2,6-Me2C6H3)}NdHal2(THF)2 (Hal = I (3), Cl (4)) were synthesized by exchange reactions of lithium and potassium amidinates with anhydrous neodymium halides NdHal3(THF)n (Hal = I, n = 3.5; Cl, n = 0). The X-ray diffraction studies showed that the new compounds are monomeric and the amidinate ligand is tridentate. Chloride complex 4 involved in the three- and four-component catalyst systems 4–AlR3–[Ph3C] [B(C6F5)4] (1: 10: 1; AlR3 = AlBui 3, AlMe3), 4–AlR3–PriOH (1: 10: 10; AlR3 = AlBui3, AlMe3), and 4–AlR3–[Ph3C][B(C6F5)4]–PriOH (1: 10: 1: 10; AlR3 = AlBui3, AlMe3) exhibits activity in stereospecific isoprene polymerization and allows the preparation of high-molecular-weight polyisoprene samples with exceptionally high cis-1,4-unit content (up to 99.4%).

Ligand-Assisted Back Energy Transfer in Luminescent TbIII Complexes for Thermosensing Properties.

A luminescent TbIII complex with a hexafluoroacetylacetone (hfa) ligand shows a characteristic back energy transfer (BEnT), which leads to high temperature sensitivity and potential application as a thermosensitive paint. Ligand-assisted BEnT was observed when a phosphine oxide ligand was introduced into Tb(hfa)3 complex, which was shown to affect the activation energy (ΔEa ) and frequency factor (A) in the BEnT process between TbIII ion and hfa ligands. According to temperature-dependent emission-lifetime measurements of mononuclear Tb(hfa)3 complexes with monodentate phosphine oxides and polynuclear Tb(hfa)3 complexes with bidentate phosphine oxides, the ΔEa and A values of polynuclear TbIII complexes were smaller than those of mononuclear TbIII complexes. Phosphorescence spectra and lifetimes of each Gd(hfa)3 complex revealed that excited states of hfa ligands in TbIII complexes differed from those of the polynuclear TbIII complexes and mononuclear TbIII complexes. The differences in the ΔEa and A values between polynuclear and mononuclear TbIII complexes were caused by the formation of different excited states, such as delocalization of the excited state in the polynuclear TbIII complexes and localization of excited states in the mononuclear TbIII complexes. In particular, small ΔEa and A values of polynuclear TbIII complexes provided high, effective activation of the BEnT at low temperature, which resulted in high-sensitive temperature-dependent phosphor materials over a wide temperature range.

Optical Temperature Sensors Based On Europium(III) Beta‐Diketonate Complexes Chemically Bonded To Functionalized Polydimethylsiloxane

AbstractNew luminescent temperature probes were synthesized based on the dispersion of the europium(III) [Eu(tta)3(H2O)2] complex (tta=thenoyltrifluoroacetonate), and the covalent bond of europium(III) [Eu(tta)3(adppo)(H2O)] and [Eu(tta)3(adppo)2] (adppo=allyldiphenylphosphine oxide) complexes by the hydroslylilation reaction between the allyl group and the hydride terminal polydimethylsiloxane (PDMS). Phosphine oxide coordination to the europium(III) ion increases the lifetime values and changes the emission profile to a more symmetrical europium(III) chemical environment. The membranes shows a decrease in lifetime values with the increase of temperature, and the dynamic range of the luminescent membranes shifts to higher temperatures by successive substitution of water molecules for the phosphine oxide ligand. Sensitivities of 6.76, 7.80 and 8.35 μS C−1 were obtained for the membranes containing the [Eu(tta)3(H2O)2], [Eu(tta)3(adppo)(H2O)] and [Eu(tta)3(adppo)2] complexes, respectively. Low oxygen cross sensitivity are observable in the membranes containing the coordinated adppo molecule, allowing their use in multiparametric sensors.

Chemoselective Catalytic Dehydrogenative Cross-Coupling of 2-Acylimidazoles: Mechanistic Investigations and Synthetic Scope

Chemoselective iron-catalyzed dehydrogenative cross-coupling using 2-acylimidazoles is described. The addition of a phosphine oxide ligand substantially facilitated the generation of tert-butoxy radicals from di-tert-butyl peroxide, allowing for efficient benzylic C–H bond cleavage under mild conditions. Extensive mechanistic studies revealed that the enolization of 2-acylimidazole proceeded through dual iron catalyst activation, followed by subsequent chemoselective cross-coupling with a benzyl radical over an undesired benzyl radical-derived homocoupling dimer that inevitably formed in earlier reported conditions. A variety of alkylarenes, aliphatic alkane, and functionalized 2-acylimidazoles were applicable, demonstrating the synthetic utility of the present catalysis. Contiguous all-carbon quaternary carbons were constructed through dehydrogenative cross-coupling. The catalytic chemoselective activation of 2-acylimidazole over bidentate coordinative and much more acidic malonate diester was particular noteworthy. Catalytic oxidative cross-enolate coupling of two distinct carboxylic acid equivalents was also achieved using acetonitrile as a coupling partner.

Recent advances in Ni−Al bimetallic catalysis for unreactive bond transformation

Ni−Al bimetallic catalysis proves to be an efficient catalytic strategy for unreactive bond transformations. Recently, chiral bifunctional ligands, especially amphoteric secondary phosphine oxide (SPO) ligand, are used for a more powerful synergistic effect in the bimetal-catalyzed reactions, providing not only milder reaction conditions and higher reactivity but also excellent reaction selectivity. Herein, we give a brief review on the development of Ni−Al bimetallic catalytic system and highlight recent advances in enantioselective Ni−Al bimetallic catalysis for unreactive bond transformation.

Highly Efficient Removal of Uranium from Aqueous Solution Using a Magnetic Adsorbent Bearing Phosphine Oxide Ligand: A Combined Experimental and Density Functional Theory Study

It is still a great challenge to develop magnetic adsorbents for the highly efficient entrapment of uranium from aqueous solution. Herein, a novel magnetic adsorbent (denoted as Fe3O4/P (AA-MMA-DVP)) bearing phosphine oxide ligand was designed and synthesized via a DPE (1,1-diphenylethylene) method based on DPE as radical controlling agent, showing an excellent adsorption capacity for uranium at pH 4.5 and outstanding selectivity in aqueous media including 14 coexisting ions. The magnetic adsorbent showed a qmax value of 413.2 mg g–1 at 298 K and pH 4.5, which was higher than that of most of other magnetic adsorbents. The outstanding selectivity (Su = 95.8%) for uranium was reasonably ascribed to the strong complexation between UO22+ and P═O groups anchored on the polymer skeletion, which was evidenced by experimental results. Furthermore, the magnetic adsorbent could be isolated by magnetic force and be recycled at least five times without significant loss in adsorption capacity. This work provided a con...

Palladium‐Catalyzed C2−H Arylation of Unprotected (N−H)‐Indoles “On Water” Using Primary Diamantyl Phosphine Oxides as a Class of Primary Phosphine Oxide Ligands

AbstractWe present the Pd‐catalyzed arylation of (N−H)‐indoles with functionalized haloarenes “on water” using hitherto untested primary diamantyl phosphine oxides (PPO) as ligands. Remarkable C2−H arylation selectivity was achieved by employing functionalized iodoarenes and N‐unprotected indoles. We provide evidence that the in situ generated oxide of (9‐hydroxydiamant‐4‐yl)phosphine L1 is key for the reaction efficiency by comparing a set of diamantane‐based compounds structurally related to L1. Our results demonstrate the power of the new PPO ligands for the C−H functionalization of unprotected (N−H)‐heterocycles.

Two Cd(II) coordination polymers based on tris(p-carboxylphenyl)phosphine oxide accompanied by in situ ligand formation

Two Cd(II) coordination polymers constructed from tris(p-carboxylphenyl)phosphine oxide (H3TPO), [Cd(HTPO)(1,4-bix)·3H2O]n (1) and [Cd2(HTPO)(HBPO)(H2O)2]n (2) (1,4-bix = 1,4-bis(imidazol-1-ylmethyl)benzene, H3BPO = bis(4-carboxylphenyl)phosphinic acid), were synthesized and identified by IR, elemental analysis, and single-crystal X-ray diffraction analysis. The 1,4-bix ligand leads to 1 as a ladder-like 1D chain structure. In 2, adjacent Cd2 units are bridged by HBPO2– and HTPO2– ligands to form a 3D structure. The H3BPO ligand is formed from the in situ reaction of H3TPO. It is the first example from hydrated Cd(II) salt promoting partial hydrolysis of a phosphine oxide ligand. The thermal behavior and solid-state photoluminescence properties correlated with the corresponding structural features were investigated.