Anti Configuration Research Articles

Diiridium(III) Complexes with Fluorenylpyridyl Cyclometalating and μ2‐Oxamidato Bridging Ligands and their High Efficiency Phosphorescent Solution‐Processed OLEDs

Three neutral diiridium(III) complexes with 2‐fluorenylpyridyl (flpy) or 5‐fluoro‐2‐fluorenylpyridyl (flpyF) as C^N cyclometalating ligands and a μ2‐oxamidato bridge have been synthesized. NMR spectroscopy shows that the complexes are inseparable mixtures of diastereomers (rac, DD/LL and meso, DL) with bridges in anti and syn configurations. Each isomer was determined using 19F NMR data on the flpyF complex. Single crystal diffraction studies of two complexes revealed meso diastereomers with anti configuration of the bis‐(t‐butylphenyl)oxamidato bridge but an uncertain configuration of the unsubstituted μ2‐oxamidato bridge. The complexes are highly emissive (ΦPL 57‐82% in solution) with excited state lifetimes of tp ca. 40 ms. The vibronic emissions with maxima at 553‐561 nm and at 587‐595 nm in solution are attributed to mixed metal‐ligand to ligand charge transfer (3MLLCT). Density functional theory (DFT) and time dependent‐DFT (TD‐DFT) calculations establish the involvement of the fluorenyl groups and the vibronic structures in the emissions. The bridge mediates intramolecular interactions between iridium centers based on electrochemical measurements Phosphorescent organic light‐emitting diodes (PhOLEDs) using these complexes as the emissive dopants with a solution‐processed active layer have bright greenish‐yellow emission with lmaxEL ca. 560 nm, luminous efficiency up to 26 cd/A and high external quantum efficiency (maximum hext ca. 20%).

The role of hydrogen bonding in the conformational stability of 2-methoxyresorcinol: Insights from theoretical calculations, SERS spectroscopy, and solvent effect

Resorcinol derivatives exhibit unique structural and electronic features. The presence of two hydroxyl groups, along with other substituents, can greatly impact these molecules’ conformational profile and vibrational characteristics. This work investigates molecular and electronic properties of 2-methoxyresorcinol (2-MR) by combining quantum-chemical and spectroscopic techniques. The molecule of 2-MR can exist in the syn, anti, and anti–syn configurations, depending on the orientation of the hydroxyl groups. The syn and anti–syn forms have been verified from DFT, MP2 and MP4 (SDQ) calculations and from infrared/Raman spectroscopy to be stabilized by intramolecular hydrogen bonding that takes place between the hydrogen atoms of the OH groups and the methoxy moiety’s oxygen atom. Such an interaction results in 6–7 kcal/mol more stable states than the corresponding anti-configuration, where only steric forces control the molecule stability. The effect of different solvents on the Raman features has also been accessed. Unlike other solutions, aqueous 2-MR facilitated a split in the OH stretching peak, which can be attributed to the pronounced solute–solvent intermolecular forces through the OH groups. Surface-enhanced Raman scattering (SERS) spectroscopic analysis of trace 2-MR utilizing as-synthesized silver nanoparticles shows a remarkable boost in the Raman signal intensities of several vibrational modes. The SERS detection exhibits a wide dynamic range and a detection limit of 1 × 10−8 M.

NIS-Promoted Chemodivergent and Diastereoselective Synthesis of Pyrrolinyl and Cyclopentenyl Spiropyrazolones via Regulated Cyclization of Alkylidene Pyrazolones with Enamino Esters.

An N-iodosuccinimide-promoted annulation of alkylidene pyrazolones with enamino esters has been explored to construct a spiropyrazolone moiety through a Michael addition/iodination/intramolecular nucleophilic substitution sequence. When the reaction was performed in acetonitrile at 100 °C, it furnished pyrrolinyl spiropyrazolones exclusively in an anti configuration through N-attacking cyclization. When the reaction was performed in dimethyl sulfoxide at 80 °C in the presence of K2HPO4, it afforded cyclopentenyl spiropyrazolones exclusively in the syn configuration through C-attacking cyclization. A plausible mechanism has also been proposed.

Crystal structure of the photosensory module from a PAS-less cyanobacterial phytochrome as Pr shows a mix of dark-adapted and photoactivated features

Phytochromes (Phys) are a diverse collection of photoreceptors that regulate numerous physiological and developmental processes in microorganisms and plants through photointerconversion between red-light absorbing Pr and far-red light-absorbing Pfr states. Light is detected by an N-terminal photosensing module (PSM) sequentially comprised of Period/ARNT/Sim (PAS), cGMP-phosphodiesterase/adenylyl cyclase/FhlA (GAF), and Phy-specific (PHY) domains, with the bilin chromophore covalently-bound within the GAF domain. Phys sense light via the Pr/Pfr ratio measured by light-induced rotation of the bilin D-pyrrole ring that triggers conformational changes within the PSM, which for microbial Phys reaches into an output region. A key step is a β-stranded to α-helical reconfiguration of a hairpin loop extending from the PHY domain to contact the GAF domain. Besides canonical Phys, cyanobacteria express several variants, including a PAS-less subfamily that harbors just the GAF and PHY domains for light detection. Prior 2D-NMR studies of a model PAS-less Phy from Synechococcus_sp._JA-2-3B'a(2-13) (SyB-Cph1) proposed a unique photoconversion mechanism involving an A-pyrrole ring rotation, while magic-angle-spinning NMR probing the chromophore proposed the prototypic D-ring flip. To help solve this conundrum, we determined the crystallographic structure of the GAF-PHY region from SyB-Cph1 as Pr. Surprisingly, this structure differs from canonical Phys by having a Pr ZZZsyn,syn,anti bilin configuration but shifted to the activated position in the binding pocket with consequent folding of the hairpin loop to α-helical, an architecture common for Pfr. Collectively, the PSM of SyB-Cph1 as Pr displayed a mix of dark-adapted and photoactivated features whose co-planar A-C pyrrole rings supports a D-ring flip mechanism.

Adenine Methylation Enhances the Conformational Flexibility of an RNA Hairpin Tetraloop.

The N6-methyladenosine modification is one of the most abundant post-transcriptional modifications in ribonucleic acid (RNA) molecules. Using molecular dynamics simulations and alchemical free-energy calculations, we studied the structural and energetic implications of incorporating this modification in an adenine mononucleotide and an RNA hairpin structure. At the mononucleotide level, we found that the syn configuration is more favorable than the anti configuration by 2.05 ± 0.15 kcal/mol. The unfavorable effect of methylation was due to the steric overlap between the methyl group and a nitrogen atom in the purine ring. We then probed the effect of methylation in an RNA hairpin structure containing an AUCG tetraloop, which is recognized by a "reader" protein (YTHDC1) to promote transcriptional silencing of long noncoding RNAs. While methylation had no significant conformational effect on the hairpin stem, the methylated tetraloop showed enhanced conformational flexibility compared to the unmethylated tetraloop. The increased flexibility was associated with the outward flipping of two bases (A6 and U7) which formed stacking interactions with each other and with the C8 and G9 bases in the tetraloop, leading to a conformation similar to that in the RNA/reader protein complex. Therefore, methylation-induced conformational flexibility likely facilitates RNA recognition by the reader protein.

Reining in Radium for Nuclear Medicine: Extra-Large Chelator Development for an Extra-Large Ion.

Targeted α therapy (TAT) of soft-tissue cancers using the α particle-emitting radionuclide 223Ra holds great potential because of its favorable nuclear properties, adequate availability, and established clinical use for treating metastatic prostate cancer of the bone. Despite these advantages, the use of 223Ra has been largely overshadowed by other α emitters due to its challenging chelation chemistry. A key criterion that needs to be met for a radionuclide to be used in TAT is its stable attachment to a targeting vector via a bifunctional chelator. The low charge density of Ra2+ arising from its large ionic radius weakens its electrostatic binding interactions with chelators, leading to insufficient complex stability in vivo. In this study, we synthesized and evaluated macropa-XL as a novel chelator for 223Ra. It bears a large 21-crown-7 macrocyclic core and two picolinate pendent groups, which we hypothesized would effectively saturate the large coordination sphere of the Ra2+ ion. The structural chemistry of macropa-XL was first established with the nonradioactive Ba2+ ion using X-ray diffraction and X-ray absorption spectroscopy, which revealed the formation of an 11-coordinate complex in a rare anti pendent-arm configuration. Subsequently, the stability constant of the [Ra(macropa-XL)] complex was determined via competitive cation exchange with 223Ra and 224Ra radiotracers and compared with that of macropa, the current state-of-the-art chelator for Ra2+. A moderate log KML value of 8.12 was measured for [Ra(macropa-XL)], which is approximately 1.5 log K units lower than the stability constant of [Ra(macropa)]. This relative decrease in Ra2+ complex stability for macropa-XL versus macropa was further probed using density functional theory calculations. Additionally, macropa-XL was radiolabeled with 223Ra, and the kinetic stability of the resulting complex was evaluated in human serum. Although macropa-XL could effectively bind 223Ra under mild conditions, the complex appeared to be unstable to transchelation. Collectively, this study sheds additional light on the chelation chemistry of the exotic Ra2+ ion and contributes to the small, but growing, number of chelator development efforts for 223Ra-based TAT.

Structural Diversity in Cyclometalated Diiridium(III) Complexes with Bridging syn and anti μ2‐Oxamidato and μ2‐Dithioxamidato Ligands

AbstractSix new diiridium complexes containing 2‐methyl‐6‐phenylpyridyl as the cyclometalating ligand with a μ2‐oxamidato or a μ2‐dithioxamidato ligand as the bridge have been synthesized in 60–73 % yields. These complexes were revealed by multinuclear NMR spectroscopy to contain inseparable mixtures of diastereomers (rac, ΔΔ/ΛΛ and meso, ΔΛ) with bridges in anti and syn configurations. The remarkable variety of isomers present was confirmed by X‐ray crystallography on single crystals grown from mixtures of each complex. In one complex with a N,N’‐bis(4‐trifluoromethylphenyl)‐μ2‐oxamidato bridge, two single crystals of anti and syn isomers were structurally determined. Two single crystals of the μ2‐dithioxamidato bridge complex were found to contain rac and meso forms of the syn isomer. Hybrid DFT computations on the four isomers of each diiridium complex revealed negligible energetic preferences for one isomer despite the methyl groups in the 2‐methyl‐6‐phenylpyridyl cyclometalating ligands being close to the neighboring methyl groups and the bridge, thus supporting the experimental findings of isomer mixtures. Two distinct broad emissions with maxima at 522–529 nm and at 689–701 nm observed in these complexes in dichloromethane are attributed to mixed metal‐ligand to ligand charge transfer (MLLCT) excited states involving the pyridyl and bridge moieties respectively with the aid of electronic structure computations.

Stereospecific Synthesis of Cyclohexenone Acids by [3,3]-Sigmatropic Rearrangement Route.

Herein we report a modular synthetic method for the preparation of diaryl-substituted cyclohexenone acids starting from phenyl pyruvate and suitable enones. When the reaction is carried out in alkaline tert-butanol or toluene solutions in microwave-assisted conditions mainly anti configuration products are obtained with up to 86% isolated yield. However, when the reaction is carried out in alkaline water, a mixture of products with anti and syn conformations is obtained with up to 98% overall isolated yield. Mechanistically the product with anti conformation forms by a hemiketal-oxy-Cope type [3,3]-sigmatropic rearrangement-intramolecular aldol condensation route and syn product by an intermolecular aldol condensation-electrocyclization (disrotatory type) route.

Spectroscopic and DFT Study of Alizarin Red S Complexes of Ga(III) in Semi-Aqueous Solution

A combined spectroscopic and computational approach has been used to study in detail the complexation between Ga(III) and ARS in solution. The NMR results revealed the formation of four Ga(III)/ARS complexes, at pH 4, differing in their metal:ligand stoichiometries or configuration, and point to a coordination mode through the ligand positions C-1 and C-9. For equimolar metal:ligand solutions, a 1:1 [Ga(ARS)(H2O)4]+ complex was formed, while for 1:2 molar ratio solutions, a [Ga(ARS)2(H2O)2]− complex, in which the two ligands are magnetically equivalent, is proposed. Based on DFT calculations, it was determined that this is a centrosymmetric structure with the ligands in an anti configuration. For solutions with a 1:3 molar ratio, two isomeric [Ga(ARS)3]3− complexes were detected by NMR, in which the ligands have a mer and a fac configuration around the metal centre. The DFT calculations provided structural details on the complexes and support the proposal of a 1,9 coordination mode. The infrared spectroscopy results, together with the calculation of the infrared spectra for the theoretically proposed structures, give further support to the conclusions above. Changes in the UV/vis absorption and fluorescence spectra of the ligand upon complexation revealed that ARS is a highly sensitive fluorescent probe for the detection of Ga(III).

Methyl Effects on the Stereochemistry and Reactivity of PPP-Ligated Iron Hydride Complexes.

Iron dihydride complexes are key intermediates in many iron-catalyzed reactions. Previous efforts to study molecules of this type have led to the discovery of a remarkably stable cis-FeH2 complex, which is supported by bis[2-(diisopropylphosphino)phenyl]phosphine (iPrPPHP) along with CO. In this work, the hydrogen on the central phosphorus has been replaced with a methyl group, and the corresponding iron carbonyl dichloride, hydrido chloride, and dihydride complexes have been synthesized. The addition of the methyl group favors the anti configuration for the Me-P-Fe-H moiety and the trans geometry for the H-Fe-CO motif, which is distinctively different from the iPrPPHP system. Furthermore, it increases the thermal stability of the dihydride complex, cis-(iPrPPMeP)Fe(CO)H2 (iPrPPMeP = bis[2-(diisopropylphosphino)phenyl]methylphosphine). The variations in stereochemistry and compound stability contribute greatly to the differences between the two PPP systems in reactions with PhCHO, CS2, and HCO2H.

Enantio- and Diastereoselective Assembly of Multi-Layer Folding Chiral Targets via Asymmetric Catalytic Single C–C Bond Formation

AbstractThis work presents the first enantio- and diastereoselective assembly of multi-layer folding targets through asymmetric catalytic C–C bond formation. Pd[(S)-BINAP]Cl2 is found to be an efficient catalyst for the Suzuki–Miyaura coupling between phosphinyl bromides and benzothiadiazole boronic esters for this asymmetric assembly. The structure of the resulting chiral multi-layer folding framework is unambiguously determined by X-ray analysis and shows a nearly parallel pattern of three layers and quasi-syn and -anti configurations. Good to excellent diastereo- and enantioselectivities (up to >20:1 dr and >99:1 er) are achieved.

A metal alkynyl molecular wire with PN ligands: Synthesis, isomerization, physical properties and single-molecule conductance

As new candidates for organometallic molecular wires, we designed a ruthenium trans-di(alkynyl) molecular wire 1H, trans-Ru(PN)2(C≡CC≡C-H)2, with the two mixed phosphine-pyridine supporting ligands (PN: 2-diphenylphosphinomethyl-6-methylpyridine). While two stereo-isomers with the syn and anti configurations were possible, the syn isomers of triisopropylsilylbutadiynyl precursors syn-1TIPS and syn-1H were prepared in direct and stereo-selective manners. Electrochemical analysis of syn-1TIPS revealed a virtually reversible redox wave with the potential cathodically shifted compared to that of the bis(diphosphine) analogue 2TMS, trans-Ru(dppe)2(C≡CC≡C-SiMe3)2. The density functional theoretical (DFT) study supports the similarity of the electronic structures of 1 and 2 with the HOMOs being close to the Fermi energy level of gold electrodes. STM-break junction measurements of Au-syn-1-Au (Au: gold electrode) revealed high single-molecule conductance (1.9 × 10–2G0), which is comparable to that of Au-2-Au. Calculations on the basis of the DFT-non equilibrium Green’s function method also support the experimental results. Notably, the molecular junction Au- syn-1-Au can be formed from syn-1H through C-H activation and formation of Au-C bonds without any pre-functionalization in contrast to the bis(diphosphine) analogue 2H, which requires terminal gold functionalization.

A Tandem Semipinacol Rearrangement/Aldehyde Arylation or Alkylation of Trisubstituted 2,3-Epoxy Alcohols with Grignard Reagents for Functionalized 1,3-Diols

A tandem semipinacol rearrangement/aldehyde arylation or alkylation reaction leading to formation of functionalized 1,3-diols bearing three consecutive tertiary stereocenters is identified from the reaction of various new trisubstituted 2,3-epoxy alcohols with numerous Grignard reagents. This reaction is useful for stereoselective construction of three consecutive tertiary stereocenters. The observed 1,3-diols exist in the anti configuration, which is confirmed by two-dimensional nuclear Overhauser effect spectroscopy, the crystal structure of acetonide of 1,3-diol analogue 3ai, and further density functional theory studies.

Synthesis, Molecular and Supramolecular Structure Aspects, and Antimicrobial Activity of the Centrosymmetric [Ag(5-Nitroquinoline)2]ClO4 Complex

The new homoleptic [Ag(5-nitroquinoline)2]ClO4 centrosymmetric complex was synthesized and its structure aspects were investigated. It crystallized in the monoclinic space group C2/c with a = 10.0279(2) Å, b = 13.2295(3) Å, c = 14.7552(3) Å and β = 102.1050(10)° while V = 1913.96(7) Å3 and half molecule as asymmetric formula. The Ag(I) is coordinated with two symmetrically related 5-nitroquinoline ligand units via the heterocyclic nitrogen atom with Ag-N distance of 2.146(6) Å and N1-Ag-N1 angle of 173.0(3)°. The two coordinated 5-nitroquinoline have anti configuration to one another and the perchlorate anion is set freely uncoordinated. The only Ag…O interactions are Ag1…O2 (3.110 Å) and Ag1…O1 (3.189 Å) which occur between the Ag(I) in one complex unit and the O-atoms from the NO2 groups in the neighbouring complex units. Hence, Ag(I) has coordination number 2 and its coordination geometry is slightly bent. Hirshfeld analysis indicated that the O…H (51.1%), C…H (11.8%), H…H (10.8%) and C…C (8.9%) contacts are the most common. Exclusively, the O…H, C…O, N…O, O…O and Ag…O contacts are the only shorter contacts than the vdWs radii sum of the interacting atoms. The studied Ag(I) complex showed good antimicrobial activity. It has comparable antibacterial activity against P. vulgaris (MIC = 9.7 μg/mL) and S. aureus (39.1 μg/mL) to Gentamycin (4.8 and 9.7 μg/mL, respectively) while better antifungal activity against A. fumigatus (MIC = 39.1 μg/mL) than Ketoconazole (156.2 μg/mL).

Synthesis and Electron Accepting Properties of Two Di(benz[f]indenone)-Fused Tetraazaanthracene Isomers.

We designed and synthesized a novel di(benz[f]indenone)-fused tetraazaanthracene derivative and isolated its two isomers, 1a and 1s, having anti and syn configurations, respectively. Their structure and that of the condensation reaction intermediates, anti-2a and syn-2s, were fully characterized using one- and two-dimensional nuclear magnetic resonance spectroscopy and single-crystal X-ray diffraction. The optical and electronic properties of 1a and 1s were investigated using ultraviolet-visible absorption and fluorescence spectroscopies, cyclic voltammetry, and time-dependent density functional theory calculations. The presence of the carbonyl and ethynyltris(isopropyl)silane groups endows the di(benzoindenone)-fused azaacene derivatives with a strong electron accepting character. With an electron affinity of approximately -3.7 eV, the two isomers represent attractive electron-deficient molecular systems for the generation of n-channel semiconducting materials. Organic field effect transistors of 1a and 1s showed electron transport, and organic solar cells gave a proof of concept of the potential of the two compounds as electron acceptor materials when they are paired with an electron donor polymer.

\u03b1-Tocopherol phosphate as a photosensitizer in the reaction of nucleosides with UV light: formation of 5,6-dihydrothymidine

Introductionα-Tocopherol phosphate, a natural water-soluble α-tocopherol analog, exists in biological tissues and fluids. Synthesized α-tocopherol phosphate is used as an ingredient of cosmetics.FindingsWhen a neutral mixed solution of 2′-deoxycytidine, 2′-deoxyguanosine, thymidine, and 2′-deoxyadenosine was irradiated with UV light at wavelengths longer than 300 nm in the presence of α-tocopherol phosphate, thymidine was markedly consumed in an α-tocopherol phosphate dose-dependent manner, whereas other nucleosides only slightly decreased. Two major product peaks were detected in an HPLC chromatogram. The products were identified as diastereomers of 5,6-dihydrothymidine. The addition of radical scavengers had almost no effects on the generation of 5,6-dihydrothymidine, whereas the reactions of nucleosides other than thymidine were suppressed. Trolox, another water-soluble α-tocopherol analog, did not generate 5,6-dihydrothymidine, although all nucleosides were slightly consumed. When UV irradiation of thymidine with α-tocopherol phosphate was conducted in D2O, two deuterium atoms were added to 5 and 6 positions of thymidine with both syn and anti configurations. The ratio of syn and anti configurations alternated depending on pD of the solution.ConclusionsThe results indicate that α-tocopherol phosphate is a photosensitizer of nucleosides, especially thymidine, and that it introduces two hydrogen atoms to thymidine from H2O, generating 5,6-dihydrothymidine.

Raman Spectroscopy of an Atypical C15-E,syn Bilin Chromophore in Cyanobacteriochrome RcaE.

Cyanobacteriochromes (CBCRs) belong to the phytochrome superfamily of photoreceptors, the members of which utilize a linear tetrapyrrole (bilin) as a chromophore. RcaE is a representative member of a green/red-type CBCR subfamily that photoconverts between a green-absorbing dark state and red-absorbing photoproduct (Pr). Our recent crystallographic study showed that the phycocyanobilin (PCB) chromophore of RcaE adopts a unique C15-E,syn configuration in the Pr state, unlike the typical C15-E,anti configuration for the phytochromes and other CBCRs. Here, we measured Raman spectra of the Pr state of RcaE with 1064 nm excitation and explored the structure of PCB and its interacting residues under physiologically relevant aqueous conditions. We also performed measurements of RcaE in D2O as well as the sample reconstituted with the PCB labeled with 15N or with both 13C and 15N. The observed Raman spectra were analyzed by quantum mechanics/molecular mechanics (QM/MM) calculations together with molecular dynamics simulations. The Raman spectra and their isotope effects were well-reproduced by the simulated spectra of fully protonated PCB with the C15-E,syn configuration and allowed us to assign most of the observed bands. The present vibrational analysis of the all syn bilin chromophore using the QM/MM method will advance future studies on CBCRs and the related proteins by vibrational spectroscopy.

Synthesis of a Tetraphenyl-Substituted Dihydropentalene and Its Alkali Metal Hydropentalenide and Pentalenide Complexes

We report a high-yielding solution phase synthesis of 1,3,4,6-tetraphenyl-dihydropentalene based on a simple annulation reaction of cyclopentadiene with a chalcone. Deprotonative metalation of 1,3,4,6-tetraphenyl-dihydropentalene with alkali metal bases (Li, Na, K) of moderate basicity (pKa > 15) cleanly yields the corresponding hydropentalenide complexes, which exist as solvent-separated ion pairs in coordinating solvents such as THF, pyridine, and DMSO. A second deprotonative metalation with stronger alkali metal bases (pKa > 25) yields the double-anionic, 10 π aromatic tetraphenyl-pentalenide complexes, which are of low solubility in the case of Li2, Na2, and K2. In the solid state the two metals are bound η5 to each anionic ring in anti configuration as in the unsubstituted pentalenide Li2[C8H6]. Mixed-metal tetraphenyl-pentalenide complexes of Li/Na/K display remarkably enhanced solubility, allowing for solution phase characterization via NMR and UV–vis spectroscopy and application in transmetalation reactions.

Nickel-Templated Replacement of Phosphine Substituents in a Tetradentate Bis(amido)bis(phosphine) Ligand.

The replacement of phosphine substituents in nickel-bound PNNP ligands is reported as an alternative method for preparing multidentate phosphine ligands with alkyl substituents. Treatment of the previously reported bis(phosphide) complex {K(THF)x}22Ph[PNNP]Ni (2) with 2 equiv of MeI, iPrI, and 1,3-dibromoethane formed alkyl-substituted complexes 2Ph,2Me[PNNP]Ni (3), 2Ph,2iPr[PNNP]Ni (4), and 2Ph,propylene[PNNP]Ni (5), respectively. The stereoselectivity (racemic vs meso) of these reactions can be controlled by varying the reaction temperature. The racemic mixtures of products with the new alkyl substituents in an anti configuration were favored at lower temperatures, whereas a larger proportion of meso compounds was acquired at higher temperatures. Further treatment of 3 with KH resulted in selective elimination of the remaining phenyl groups rather than the methyl substituents, affording bis(methylphosphide) complex {K(THF)x}22Me[PNNP]Ni (6). Subsequent treatment of 6 with additional MeI formed 4Me[PNNP]Ni (7), in which all four phenyl groups were replaced with methyl substituents. As a proof of concept, demetalation of the ligand from 7 was achieved using aqueous KCN to form a free dimethylphosphine-substituted ligand H24Me[PNNP] (8), and 8 was subsequently coordinated to a different metal, using PdCl2 to form 4Me[PNNP]Pd (9). Unlike the clean elimination of phenyl substituents from 3, the reactions of KH with 4 and 5 exhibited competitive elimination of both alkyl and phenyl substituents and/or attenuated reactivity.

Synthesis, structures, DFT studies and properties of novel tertiary diphosphines based on α- and β-naphthylamine

Based on α- and β-naphthylamine, two new diphosphines, N,N-bis((diphenylphos phino)methyl)naphthalen-1-amine (1) and N,N-bis((diphenylphosphino)methyl)naphthalene -2-amine (2), have been prepared and characterized by IR, 1H NMR, 31P NMR, TG, UV-Vis, XRD and X-ray crystal structure analysis. Structural analysis shows that the two Ph2PCH2- groups in 1 and 2 are disposed in an anti configuration, and the change of the position of the (Ph2PCH2)2N-group on the naphthalene moiety results in different spatial configurations of the two Ph2P- groups and different weak interactions, such as C-H…π and π–π interactions. DFT studies show that the composition of the HOMOs for 1 and 2 are almost the same (the naphthyl group with admixed N and P atoms), but the ingredients of the LUMOs for 1 are different from that for 2, coinciding with the change of Mülliken atomic charges. Moreover, the emission spectra show that the emissions of complexes 1 and 2 in acetonitrile solution are not similar to those of solid-state samples.