A cyclometalated Pt(II)-Pt(II) clamshell dimer with a triplet emission at 887 nm.

Here, a cyclometalated Pt(II) clamshell dimer (complex 2) has been synthesized with the primary ligand of dibenzo(f,h)quinoxaline and an ancillary ligand of N,N'-diphenylformamidine. In addition, a mononuclear Pt(II) complex 1a and a binuclear Pt(II) complex 1b were also prepared. Complex 1a was coordinated by one cyclometalated ligand of dibenzo(f,h)quinoxaline, one chloride ion, and one N,N'-diphenylformamidine. Complex 1b was coordinated by one cyclometalated ligand of dibenzo(f,h)quinoxaline, two chloride ions, and two N,N'-diphenylformamidines. All of these three complexes were characterized by nuclear magnetic resonance (NMR) spectroscopy, high-resolution mass spectrometry (HRMS), elemental analyses, and single-crystal X-ray diffraction (XRD). The Pt-Pt distance in complex 2 was 2.8439(2) Å. It also exhibited a near-infrared (near-IR) emission at 887 nm in the pure solid state. On the other hand, complexes 1a and 1b exhibited triplet emission at 589 and 660 nm, respectively, in the pure solid state. Furthermore, in 2 wt% poly(Me methacrylate) (PMMA) films, complex 1a showed a triplet emission at 548 nm (with Φ = 84% and τ = 5.53 µs) and complex 1b showed an emission at 627 nm (with Φ = 79% and τ = 4.07 µs). Due to its great photophysical properties, complex 1b was deposited onto quartz plates for the detection of organic solvent vapors and it showed unique emission quenching for the vapor of tetrahydrofuran.

Platinum(II) diimine complexes containing phenylpyridine ligands decorated with anionic closo-monocarborane clusters [CB11H12].

We report three Pt(II) diimine complexes containing ancillary ligands of phenylpyridine furnished with anionic closo-monocarborane clusters [CB11H12]-. Three neutral complexes exhibit intensive phosphorescence in the solid state and complex 1 was used to detect acetonitrile vapor in a quartz plate.

Deep Blue Phosphorescence from Platinum Complexes Featuring Cyclometalated N-Pyridyl Carbazole Ligands with Monocarborane Clusters (CB11H12-).

The utilization of deep blue phosphorescent materials in high-performance displays and solid-state lighting requires high quantum efficiencies and color purities. Here, we describe the preparation and luminescent properties of novel platinum triplet emitters featuring cyclometalated N-pyridyl-carbazole ligands functionalized with closo-monocarborane clusters [CB11H12]-. All reported complexes were fully characterized by using standard small molecule techniques (UV-vis, cyclic voltammetry, nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HRMS)), and their solid-state structures were elucidated by X-ray diffraction. These platinum phosphors emit in the blue region of the visible wavelength spectrum in both the solid and solution states. Complex 4a exhibits the highest luminous efficiency at λem = 439 nm with a photoluminescent quantum yield (PLQY) of 60% by dispersing in a PMMA matrix. Electrochemical and computational studies of complexes 4a and 4b revealed that the blue phosphorescence originates mainly from intraligand 3π → π* (3ILCT) transitions with relatively small 3MLCT mixing. A deep-blue OLED containing 4a as the light-emitting dopant was successfully fabricated using a solution-processed method, and the device exhibited blue photoluminescence with CIE coordinates of (0.17, 0.15) and a maximum external quantum efficiency (EQEmax) value of 6.2%. This article represents the pioneering study of a deep blue PhOLED using a Pt complex bearing a closo-monocarborane anion substituent, providing a new avenue into the preparation of novel triplet emitters based on boron-rich cluster anions.

Green and multifunctional chitosan-based conformal coating as a controlled release platform for fruit preservation.

Food waste caused by the decay of perishable foods is a serious global issue. However, traditional preservative materials don't perform well in preventing food decay. Here, a green and multifunctional conformal coating is prepared by the hydrogen-bonding interactions among chitosan, nano-humic acid and curcumin, which is different from traditional preservative films obtained by solution blending. Thanks to the formation of hydrogen-bonding network, the surface roughness of the coating increased from 9.43 nm to 33.3 nm, which makes it more matches with the micro/nano structure of the fruit surface and obtains a good coating effect for various fruits. Furthermore, this coating shows distinctive mechanical properties (the tensile strength of 31.4 MPa), antioxidant and antibacterial activities (the inhibition zone ≥5 mm), and can be used to control the long-term release (up to 38 days) of natural preservative onto fruit surfaces. Through the demonstration of four perishable fruits, the coating can keep freshness and appearance at least 9 days longer than the uncoated samples, confirming the universal effectiveness of the coating in preventing fruit decay. This coating is easy to produce and use, washable, degradable, and makes from cheap or waste renewable biomaterials, which does not cause additional health and environmental concerns.

A 3D Analogue of Phenyllithium: Solution-Phase, Solid-State, and Computational Study of the Lithiacarborane [Li-CB11 H11 ].

The lithiacarborane [Li-CB11 H11 ]- plays a central role in carborane chemistry, as it is a key intermediate to achieve the selective functionalization of the monocarba-closo-dodecaborate [CB11 H12 ]- for applications in various fields. Also, it is an organometallic species of fundamental interest because it represents a 3D analogue of phenyllithium featuring an exo C-Li bond in addition to the delocalized negative endo charge of the spherical cluster. For the first time, the elusive and highly reactive endo/exo formal dianion [CB11 H11 ]2- has been isolated as its lithiate as well as zincate in pure form and fully characterized. DFT calculations corroborate the experimental findings and underscore the remarkably high reactivity of the lithiacarborane. Subsequent derivatizations demonstrate the relevance of its initial clean formation.

The 12-ethynylmonocarba-closo-dodecaborate anion as a versatile ligand for Cu(i) alkyne and heterobimetallic Cu(i)/M(ii) (M = Pd, Pt) alkynide complexes.

The anionic monocarborane alkyne [12-(HC[triple bond, length as m-dash]C)-CB11H11]- was employed as a ligand towards Cu(i) to form terminal alkyne complexes. Spectroscopic methods and X-ray crystallography allowed for a detailed structural analysis of complexes with nitrogen ligands, which are the first examples featuring carborane-C[triple bond, length as m-dash]CH → metal π coordination. Addition of phosphines to compound 2 afforded homoleptic Cu(i) complexes [Cu(PR3)n]+ (4), in which case the carborane becomes a non-coordinating anion. Polymeric acetylide 5 was obtained in almost quantitative yield from 2 and proved to be a suitable precursor to heterobimetallic Cu(i)/M(ii) (M = Pd, Pt) alkynide complexes with side-on and end-on coordination to the metal centers.

Highly selective palladium-catalyzed one-pot, five-fold B-H/C-H cross coupling of monocarboranes with alkenes.

Palladium-catalyzed dehydrogenative B-H/C-H cross coupling of monocarborane anions with alkenes is reported, allowing for the first time the isolation of selectively penta-alkenylated boron clusters. The reaction cascade is regioselective for the cage positions, leading directly to B2-6 functionalization. Under mild and convenient conditions, styrenes, benzylic alkenes and aliphatic alkenes are demonstrated to be viable coupling partners with exclusive vinyl-type B-C bond formation. Multiple subsequent transformations provide access to directing group-free products, chiral derivatives and penta-alkylated cages. The five-fold coupling, combined with the latter reactions, represents a powerful methodology for the straightforward synthesis of new classes of boron clusters.

Atomically Defined Monocarborane Copper(I) Acetylides with Structural and Luminescence Properties Tuned by Ligand Sterics.

The weakly coordinating cluster [CB11 H12 ]- is used as a versatile building block for the preparation of luminescent copper(I) complexes. Treatment of [CB11 H11 -12-C≡CH]- with CuI and ammonia affords {(CB11 H11 -12-C≡C)2 Cu4 (NH3 )3 }n (2). Addition of selected phosphine and pyridine ligands transforms 2 to a range of homometallic products 3-13. All compounds have been characterized by X-ray crystallography, which reveals a surprising variety of structural complexity featuring cores with two to ten Cu+ centers. In the solid state, products 3-13 exhibit room-temperature phosphorescence across the visible spectrum in colors from blue to deep red. Lifetimes at room temperature are in the microsecond regime, and quantum yields of up to Φ=0.99 are observed.

Rhodium(iii)-catalyzed dehydrogenative dialkenylation of the monocarba-closo-decaborate cluster by regioselective B-H activation.

closo-Boranes and closo-carboranes, clusters with a closed-cage structure, exhibit remarkable inertness and are unique components of products with applications in areas such as medicinal chemistry, fluorescence and materials science. Herein, we report the first transition metal-catalyzed functionalization of the mono-closo-decaborate cluster [1-CB9H10]- by regioselective B-H activation. Using terminal alkenes bearing a wide range of functional groups, dehydrogenative coupling under mild conditions leads to B2/3-dialkenylated products, as verified by X-ray crystallography and NMR studies. This substitution pattern has not been accessible by other methods and enables the straightforward synthesis of new derivatives of the {CB9} cluster.

Palladium-Catalyzed Selective Five-Fold Cascade Arylation of the 12-Vertex Monocarborane Anion by B-H Activation.

A series of cage penta-arylated carboranes have been synthesized by palladium-catalyzed intermolecular coupling of the C-carboxylic acid of the monocarba- closo-dodecaborate anion [CB11H12]- with iodoarenes by direct cage B-H bond functionalization. These transformations set a record in terms of one-pot directing group-mediated activation of inert bonds in a single molecule. The methodology is characterized by high yields, good functional group tolerance, and complete cage regioselectivity. The directing group COOH can be easily removed during or after the intermolecular coupling reaction. The mechanistic pathways were probed using density functional theory calculations. A Pd(II)-Pd(IV)-Pd(II) catalytic cycle is proposed, in which initial coupling is followed by preferred B-H activation of the adjacent boron vertex, and continuation of this selectivity results in a continuous walking process of the palladium center. The methodology opens a new avenue toward building blocks with 5-fold symmetry.

Crystal structure of a carborane endo/exo-dianion and its use in the synthesis of ditopic ligands for supramolecular frameworks.

The crystal structure of the deprotonated monocarba-closo-dodecaborate [12-CN-CB11H11]- is reported. This dianion, featuring a delocalized endohedral negative charge and an exo-cluster C-[Li] moiety, was used for the synthesis of ditopic ligands with the potential to form novel supramolecular frameworks.

Fusing Carborane Carboxylic Acids with Alkynes: 3D Analogues of Isocoumarins via Regioselective B-H Activation.

An iridium-catalyzed alkenylation/annulation sequence between monocarba-closo-dodecaborate carboxylic acids and diarylacetylenes is reported. Regioselective activation of the B2 position, followed by B-C bond formation and ring closure, affords 3D bora-analogues of isocoumarins. The reaction tolerates a variety of functional groups on the aromatic rings and can be extended to B12-substituted derivatives. Furthermore, subsequent alkenylation of the B4 vertex has been achieved in high yields.

Efficient access to amides of the carborane carboxylic acid [1-(COOH)-CB11H11].

The preparation of the carborane acid chloride [1-(COCl)-CB11H11]- from the carboxylic acid [1-(COOH)-CB11H11]- is reported. This acid chloride exhibits remarkable inertness towards moisture and can be stored under ambient conditions for several months. Reaction with amines affords secondary and tertiary carborane amides [1-(CONR1R2)-CB11H11]- in moderate to high yields under mild conditions. Two of the amide products were characterized by X-ray crystallography in addition to spectroscopic analysis. Preliminary studies show that the amides can be reduced to the corresponding amines and that the acid chloride has the potential to serve as a starting material for carborane ester formation.

Cyclic-RGD penta-peptides cRGDyK derivatized with cyclopentadienyl complexes of technetium and rhenium as radiopharmaceutical probes.

The present study reports the syntheses of half-sandwich complexes of the type [M(η5 -C5 H4 CONH-R)(CO)3 ] (M═Re,99m Tc;R═cyclic RGD peptide (cRGDyK) for potential imaging of αv ß3 integrin expression. The 99m Tc complex was prepared directly from the reaction of [99m Tc(OH2 )3 (CO)3 ]+ with cRGDyK, doubly conjugated to Thiele's acid [(C5 H5 COOH)2 ] in water. This approach extends the viability of metal-mediated retro Diels-Alder reactions for the preparation of small molecules such as linear tripeptides to a more complex cyclic peptide carrying a [(η5 -C5 H4 )99m Tc(CO)3 ] tag. The Diels-Alder product [(C5 H5 CONH-cRGDyK)2 ] was prepared from Thiele's acid via double peptide coupling. The Re-complex [Re(η5 -C5 H4 CONH-cRGDyK)(CO)3 ] was obtained by attaching [Re(η5 -C5 H4 COOH)(CO)3 ] directly to the N-terminus of cRGDyK. The identity of the 99m Tc-complex is confirmed by chromatographic comparison with the corresponding rhenium complex, fully characterized by spectroscopic techniques.

B-H functionalization of the monocarba-closo-dodecaborate anion by rhodium and iridium catalysis.

The regioselective derivatization of the monocarba-closo-dodecaborate anion via catalytic B-H bond activation is reported. Amide directing groups in combination with rhodium and iridium catalysts allowed for the direct functionalization of cage boron vertices. Products comprising B-C, B-N and B-Cl bonds were synthesized. As a key intermediate of the B-H activation step, an iridium complex with a direct B-Ir interaction was isolated and fully characterized by spectroscopic methods as well as X-ray crystallography.

Synthesis and full characterization of an iridium B-H activation intermediate of the monocarba-closo-dodecaborate anion.

The preparation and full characterization of an iridium complex of the monocarba-closo-dodecaborate anion is reported. It was prepared by B-H bond activation using a tosyl amide directing group. Analysis by spectroscopic methods and X-ray crystallography revealed the presence a direct B-Ir interaction. The carborane acts as a B,N chelating ligand towards the Ir(Cp*)(solvent) fragment, resulting in a monomeric complex that is inert in solution and the solid state. Treatment with N-chlorosuccinimide resulted in selective monochlorination of the B-Ir position. In addition, its structure, spectroscopic features and reactivity were investigated by DFT calculations.

Synthesis of tripeptide derivatized cyclopentadienyl complexes of technetium and rhenium as radiopharmaceutical probes.

We describe the syntheses of half-sandwich complexes of the type [(η(5)-Cp(CONH-R))M(CO)3] with M = Re or (99m)Tc. The R group represents different tri-peptides (tpe) which display high binding affinities for oligopeptide transporters PEPT2. The (99m)Tc complexes were prepared directly from [(99m)Tc(OH2)3(CO)3](+) and Diels-Alder dimerized, cyclopentadienyl derivatized peptides in water. This approach corroborates the feasibility of metal-mediated retro Diels-Alder reactions for the preparation of not only small molecules but also peptides carrying a [(η(5)-Cp)(99m)Tc(CO)3] tag. We synthesized the Diels-Alder product [(HCpCONH-tpe)2] from Thiele's acid [(η(5)-HCpCOOH)2] via double peptide coupling. The Re-complexes [(η(5)-CpCONH-tpe)Re(CO)3] were obtained by attaching [(Cp-COOH)Re(CO)3] directly to the N-terminus of peptides as received from SPPS. The authenticity of the (99m)Tc-complexes is confirmed by chromatographic comparison with the corresponding rhenium complexes, fully characterized by spectroscopic techniques.

Orthogonally protected artificial amino acid as tripod ligand for automated peptide synthesis and labeling with [(99m)Tc(OH(2))(3)(CO)(3)](+).

1,2-Diamino-propionic acid (Dap) is a very strong chelator for the [(99m)Tc(CO)(3)](+) core, yielding small and hydrophilic complexes. We prepared the lysine based Dap derivative l-Lys(Dap) in which the ε-NH(2) group was replaced by the tripod through conjugation to its α-carbon. The synthetic strategy produced an orthogonally protected bifunctional chelator (BFC). The -NH(2) group of the α-amino acid portion is Fmoc- and the -NH(2) of Dap are Boc-protected. Fmoc-l-Lys(Dap(Boc)) was either conjugated to the N- and C-terminus of bombesin BBN(7-14) or integrated into the sequence using solid-phase peptide synthesis (SPPS). We also replaced the native lysine in a cyclic RGD peptide with l-Lys(Dap). For all peptides, quantitative labeling with the [(99m)Tc(CO)(3)](+) core at a 10 µM concentration in PBS buffer (pH = 7.4) was achieved. For comparison, the rhenium homologues were prepared from [Re(OH(2))(3)(CO)(3)](+) and Lys(Dap)-BBN(7-14) or cyclo-(RGDyK(Dap)), respectively. Determination of integrin receptor binding showed low to medium nanomolar affinities for various receptor subtypes. The IC(50) of cyclo-(RGDyK(Dap[Re(CO)(3)])) for α(v)ß(3) is 7.1 nM as compared to 3.1 nM for nonligated RGD derivative. Biodistribution studies in M21 melanoma bearing nude mice showed reasonable α(v)ß(3)-integrin specific tumor uptake. Altogether, orthogonally protected l-Lys(Dap) represents a highly versatile building block for integration in any peptide sequence. Lys(Dap)-precursors allow high-yield (99m)Tc-labeling with [(99m)Tc(OH(2))(3)(CO)(3)](+), forming small and hydrophilic complexes, which in turn leads to peptide radiopharmaceuticals with excellent in vivo characteristics.

Chemical precipitation for controlling nitrogen loss during composting.

Aimed at controlling the nitrogen loss during composting, the mixture of magnesium hydroxide (Mg(OH)( 2)) and phosphoric acid (H(3)PO(4)) (molar ratio 1:2) were utilized as additives to avoid increasing total salinity. In trial TA, the additives were put into absorption bottles connecting with a gas outlet of fermentor (ex situ method); in trial TB, the additives were directly added to the composting materials (in situ method). During the 26 day composting period, the temperature, pH, total organic carbon (TOC), total nitrogen (TN), ammonium nitrogen (NH(4)(+)-N), total phosphorus (TP), available phosphorus (AP) and germination index (GI) were measured. The experimental results show that the additives reduced the pH, while NH( 4)(+)-N and TN were obviously improved. NH(4)( +)-N was 11.9 g kg(-1) and 3 g kg(- 1) in amended compost trial (TB) and unamended compost trial (TA), respectively; TN increased from 26.5 g kg(-1) to 40.3 g kg(-1) in TB and increased from 26.5 g kg( -1) to 26.8 g kg(-1) in TA. Analysis of the TOC and carbon mass revealed that absorbents accelerated the degradation of organic matter. The germination index test showed the maturity of TB (102%) was better than TA (82%) in final compost. Furthermore, TP and AP were also obviously improved. X-ray diffraction analysis of precipitation showed that the precipitation in absorption bottle of TA was newberyite (MgHPO( 4) 3H(2)O), however, the crystal in the TB compost was struvite (MgNH(4)PO(4) 6H(2)O: magnesium ammonium phosphate). These results indicated that Mg(OH)(2) and H(3)PO( 4) could reduce the ammonia emission by struvite crystallization reaction. Optimal conditions for struvite precipitation should be determined for different systems.