Luminescent Benzoquinolate‐Isocyanide Platinum(II) Complexes: Effect of Pt⋅⋅⋅Pt and π⋅⋅⋅π Interactions on their Photophysical Properties

The neutral compounds [Pt(bzq)(CN)(CNR)] (R=tBu ( 1 ), Xyl ( 2 ), 2‐Np ( 3 ); bzq= benzoquinolate, Xyl=2,6‐dimethylphenyl, 2‐Np=2‐napthyl) were isolated as the pure isomers with a trans‐C_bzq,CNR configuration, as confirmed by ¹³C{¹H} NMR spectroscopy in the isotopically marked [Pt(bzq)(¹³CN)(CNR)] (R=tBu ( 1′ ), Xyl ( 2′ ), 2‐Np ( 3′ )) derivatives (δ¹³C_CN≈110 ppm; ¹J(Pt,¹³C)≈1425 Hz]. By contrast, complex [Pt(bzq)(C≡CPh)(CNXyl)] ( 4 ) with a trans‐N_bzq,CNR configuration, has been selectively isolated from [Pt(bzq)Cl(CNXyl)] (trans‐N_bzq,CNR) using Sonogashira conditions. X‐ray diffraction studies reveal that while 1 adopts a columnar‐stacked chain structure with Pt–Pt distances of 3.371(1) Å and significant π???π interactions (3.262 Å), complex 2 forms dimers supported only by short Pt???Pt (3.370(1) Å) interactions. In complex 4 the packing is directed by weak bzq???Xyl and bzq???C≡E (C, N) interactions. In solid state at room temperature, compounds 1 and 2 both show a bright red emission (?=42.1 % 1 , 57.6 % 2 ). Luminescence properties in the solid state at 77 K and concentration‐dependent emission studies in CH₂Cl₂ at 298 K and at 77 K are also reported for 1 , 1·CHCl3 , 2 , 2' , 2·CHCl3 , 3 , 4 .     

Structure determination of three furan‐substituted benzimidazoles and calculation of π–π and C—H...π interaction energies

The synthesis and structural characterization of 2‐(furan‐2‐yl)‐1‐(furan‐2‐ylmethyl)‐1H‐benzimidazole [C₁₆H₁₂N₂O₂, (I)], 2‐(furan‐2‐yl)‐1‐(furan‐2‐ylmethyl)‐1H‐benzimidazol‐3‐ium chloride monohydrate [C₁₆H₁₃N₂O₂⁺·Cl⁻·H₂O, (II)] and the hydrobromide salt 5,6‐dimethyl‐2‐(furan‐2‐yl)‐1‐(furan‐2‐ylmethyl)‐1H‐benzimidazol‐3‐ium bromide [C₁₈H₁₇N₂O₂⁺·Br⁻, (III)] are described. Benzimidazole (I) displays two sets of aromatic interactions, each of which involves pairs of molecules in a head‐to‐tail arrangement. The first, denoted set (Ia), exhibits both intermolecular C—H...π interactions between the 2‐(furan‐2‐yl) (abbreviated as Fn) and 1‐(furan‐2‐ylmethyl) (abbreviated as MeFn) substituents, and π–π interactions involving the Fn substituents between inversion‐center‐related molecules. The second, denoted set (Ib), involves π–π interactions involving both the benzene ring (Bz) and the imidazole ring (Im) of benzimidazole. Hydrated salt (II) exhibits N—H...OH₂...Cl hydrogen bonding that results in chains of molecules parallel to the a axis. There is also a head‐to‐head aromatic stacking of the protonated benzimidazole cations in which the Bz and Im rings of one molecule interact with the Im and Fn rings of adjacent molecules in the chain. Salt (III) displays N—H...Br hydrogen bonding and π–π interactions involving inversion‐center‐related benzimidazole rings in a head‐to‐tail arrangement. In all of the π–π interactions observed, the interacting moieties are shifted with respect to each other along the major molecular axis. Basis set superposition energy‐corrected (counterpoise method) interaction energies were calculated for each interaction [DFT, M06‐2X/6‐31+G(d)] employing atomic coordinates obtained in the crystallographic analyses for heavy atoms and optimized H‐atom coordinates. The calculated interaction energies are −43.0, −39.8, −48.5, and −55.0 kJ mol⁻¹ for (Ia), (Ib), (II), and (III), respectively. For (Ia), the analysis was used to partition the interaction energies into the C—H...π and π–π components, which are 9.4 and 24.1 kJ mol⁻¹, respectively. Energy‐minimized structures were used to determine the optimal interplanar spacing, the slip distance along the major molecular axis, and the slip distance along the minor molecular axis for 2‐(furan‐2‐yl)‐1H‐benzimidazole.     

η4‐HBCC‐σ,π‐Borataallyl Complexes of Ruthenium Comprising an Agostic Interaction

Thermolysis of [Cp*Ru(PPh₂(CH₂)PPh₂)BH₂(L₂)] 1 (Cp*=η⁵‐C₅Me₅; L=C₇H₄NS₂), with terminal alkynes led to the formation of η⁴‐σ,π‐borataallyl complexes [Cp*Ru(μ‐H)B{R‐C=CH₂}(L)₂] ( 2 a – c ) and η²‐vinylborane complexes [Cp*Ru(R‐C=CH₂)BH(L)₂] ( 3 a – c ) ( 2 a , 3 a : R=Ph; 2 b , 3 b : R=COOCH₃; 2 c , 3 c : R=p‐CH₃‐C₆H₄; L=C₇H₄NS₂) through hydroboration reaction. Ruthenium and the HBCC unit of the vinylborane moiety in 2 a – c are linked by a unique η⁴‐interaction. Conversions of 1 into 3 a – c proceed through the formation of intermediates 2 a – c . Furthermore, in an attempt to expand the library of these novel complexes, chemistry of σ‐borane complex [Cp*RuCO(μ‐H)BH₂L] 4 (L=C₇H₄NS₂) was investigated with both internal and terminal alkynes. Interestingly, under photolytic conditions, 4 reacts with methyl propiolate to generate the η⁴‐σ,π‐borataallyl complexes [Cp*Ru(μ‐H)BH{R‐C=CH₂}(L)] 5 and [Cp*Ru(μ‐H)BH{HC=CH‐R}(L)] 6 (R=COOCH₃; L=C₇H₄NS₂) by Markovnikov and anti‐Markovnikov hydroboration. In an extension, photolysis of 4 in the presence of dimethyl acetylenedicarboxylate yielded η⁴‐σ,π‐borataallyl complex [Cp*Ru(μ‐H)BH{R‐C=CH‐R}(L)] 7 (R=COOCH₃; L=C₇H₄NS₂). An agostic interaction was also found to be present in 2 a – c and 5 – 7 , which is rare among the borataallyl complexes. All the new compounds have been characterized in solution by IR, ¹H, ¹¹B, ¹³C NMR spectroscopy, mass spectrometry and the structural types were unequivocally established by crystallographic analysis of 2 b , 3 a – c and 5 – 7 . DFT calculations were performed to evaluate possible bonding and electronic structures of the new compounds.     

Aromatic Ring‐Fused Carborane‐Based Luminescent π‐Conjugated Polymers

A series of π‐conjugated polymers linked by benzocarborane (1,2‐(buta‐1′,3′‐diene‐1′,4′‐diyl)‐1,2‐dicarbadodecaborane) were synthesized via Sonogashira–Hagihara polycondensation reaction. The opened molecular structure of diiodo monomer containing benzocarborane resulted in fast polymerization and high molecular weights. The obtained polymers were fully characterized by ¹H, ¹³C, and ¹¹B NMR spectroscopies. UV‐vis absorption and photoluminescence studies revealed the acceptor‐profile of benzocarborane. Unlike the polymers linked by o‐carborane, these polymers exhibited strong luminescence in the solution state, presumably because the inductive effect of carborane is dominant, rather than cage‐π interactions.

     

Regiodirected Synthesis and Stereochemistry of 2,4,8‐Trialkyl‐3‐thia‐1,5‐diazabicyclo[3.2.1]octanes and α,ω‐Bis(2,4,6‐trialkyl‐1,3,5‐dithiazinane‐5‐yl)alkanes

2,4,8‐Trialkyl‐3‐thia‐1,5‐diazabicyclo[3.2.1]octanes have been obtained by the regioselective and stereoselective cyclocondensation of 1,2‐ethanediamine with aldehydes RCHO (R═Me, Et, Prⁿ, Buⁿ, Pentⁿ) and H₂S at molar ratio 1:3:2 at 0°C. The increase in molar ratio of thiomethylation mixture RCHO–H₂S (6:4) at 40°C resulted in selective formation of bis‐(2,4,6‐trialkyl‐1,3,5‐dithiazinane‐5‐yl)ethanes. Cyclothiomethylation of aliphatic α,ω‐diamines with aldehydes RCHO (R═Me, Et) and H₂S at molar ratio 1:6:4 and at 40°С led to α,ω‐bis(2,4,6‐trialkyl‐1,3,5‐dithiazinane‐5‐yl)alkanes. Stereochemistry of 2,4,8‐trialkyl‐3‐thia‐1,5‐diazabicyclo[3.2.1]octanes have been determined by means of ¹H and ¹³С NMR spectroscopy and further supported by DFT calculations at the B3LYP/6‐31G(d,p) level. The structure of α,ω‐bis(2,4,6‐trialkyl‐1,3,5‐dithiazinane‐5‐yl)alkanes was confirmed by single‐crystal X‐ray diffraction study.     

Gold(III) π‐Allyl Complexes

Gold(III) π‐complexes have been authenticated recently with alkenes, alkynes, and arenes. The key importance of Pd^II π‐allyl complexes in organometallic chemistry (Tsuji–Trost reaction) prompted us to explore gold(III) π‐allyl complexes, which have remained elusive so far. The (P,C)Au^III(allyl) and (methallyl) complexes 3 and 3′ were readily prepared and isolated as thermally and air‐stable solids. Spectroscopic and crystallographic analyses combined with detailed DFT calculations support tight quasi‐symmetric η³‐coordination of the allyl moiety. The π‐allyl gold(III) complexes are activated towards nucleophilic additions, as substantiated with β‐diketo enolates.     

Isothiourea‐based lewis pairs for homopolymerization and copolymerization of 2,2‐dimethyltrimethylene carbonate with ε‐caprolactone and ω‐pentadecalactone

In this study, the homopolymerization of 2,2‐dimethyltrimethylene carbonate (DTC) and its copolymerizations with ε‐caprolactone (CL) were carried out in detail using the isothiourea‐based Lewis pairs comprised 2,3,6,7‐tetrahydro‐5H‐thiazolo(3,2‐a)pyrimidine and magnesium halides (MgX₂) with benzyl alcohol (BnOH) as the initiator. The copolymerization of DTC and CL via one‐pot addition produced randomly sequenced copolymers. On the other hand, a well‐defined linear poly(ε‐caprolactone)–block–poly(2,2‐dimethyltrimethylene carbonate) (PCL‐b‐PDTC) diblock copolymer was prepared by simple sequential ring‐opening polymerization of CL and DTC. In addition, poly(ω‐pentadecalactone)–block–PDTC diblock copolymer was successfully prepared by the same strategy. Moreover, PDTC–poly(ethylene glycol) (PEG)–PDTC triblock copolymer was synthesized in the presence of PEG 2000. The effects of different polymerization conditions on the polymerization reactions have been systematically discussed. The resulting polymers were characterized by the ¹H and ¹³C NMR spectra, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐ToF MS). The block copolyester structures were confirmed by the ¹³C NMR spectroscopy and DSC characterizations. These results indicated that the supposed mechanism was a dual catalytic mechanism. The proposed mechanism involved activation of the monomer via coordination to the MgX₂, and the initiator alcohol was deprotonated by base. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2349–2355     

Synthesis of 1‐substituted 5‐aryl‐3‐(3‐coumarinyl)‐2‐pyrazolines by the reaction of 3‐aryl‐1‐(3‐coumarinyl)propen‐1‐ones with hydrazines

1‐Acetyl‐ and 1‐propionyl‐2‐pyrazolines 11‐27 have been synthesized by the reaction of (3‐coumarinyl)chalcones 1‐10 with hydrazine in hot acetic acid or propionic acid. While 5‐aryl‐3‐(3‐coumarinyl)‐1‐phenyl‐2‐pyrazolines 28‐35 have been prepared by the reaction of (3‐coumarinyl)chalcones 1,3,5‐10 with phenylhydrazine in hot pyridine. Structures of all new compounds have been elucidated by microanalyses, ¹H and ¹³C nmr spectroscopies.     

On the π‐Electron Distribution in Biphenylene Analogues

The bonding situation in a series of biphenylene analogues – benzo[b]biphenylene and its dication, 4,10‐dibromobenzo[b]biphenylene, naphtho[2,3‐b]biphenylene and its dianion, benzo[a]biphenylene, (biphenylene)tricarbonylchromium, benzo[3,4]cyclobuta[1,2‐c]thiophene, benzo[3,4]cyclobuta[1,2‐c]thiophene 2‐oxide, benzo[3,4]cyclobuta[1,2‐c]thiophene 2,2‐dioxide, 4,10‐diazabenzo[b]biphenylene, biphenylene‐2,3‐dione, benzo[3,4]cyclobuta[1,2‐b]anthracene‐6,11‐dione, and 3,4‐dihydro‐2H‐benzo[3,4]cyclobuta[1,2]cycloheptene – where one of the two benzo rings of biphenylene is replaced by a different π‐system (B) was investigated on the basis of the NMR parameters of these systems. From the vicinal ¹H,¹H spin‐spin coupling constants, the electronic structure of the remaining benzo ring (A) is derived via the Q‐value method. It is found that increasing tendency of B to tolerate exocyclic double bonds at the central four‐membered ring of these systems favors increased π‐electron delocalization in the A ring. The analysis of the chemical shifts supports this conclusion. NICS (nucleus‐independent chemical shift) values as well as C,C bond lengths derived from ab initio calculations are in excellent agreement with the experimental data. The charged systems benzo[b]biphenylene dication and naphtho[2,3‐b]biphenylene dianion ( 7 ²⁻) are also studied by ¹³C NMR measurements. The charge distribution found closely resembles the predictions of the simple HMO model and reveals that 7 ²⁻ can be regarded as a benzo[3,4]cyclobuta[1,2‐b]‐substituted anthracene dianion. It is shown that the orientation of the tricarbonylchromium group in complexes of benzenoid aromatics can be derived from the vicinal ¹H,¹H coupling constants.     

Self‐Assembly of Dialkyltin Moieties and Mercaptobenzoic Acid into Macrocyclic Complexes with Hydrophobic “Pseudo‐Cage” or Double‐Cavity Structures: Supramolecular Infrastructures Involving Intermolecular C?H⋅⋅⋅S Weak Hydrogen Bonds and π–π Interactions

Four novel organotin complexes of two types—[R₂Sn(o‐SC₆H₄CO₂)]₆ (R=Me, 1 ?H₂O; nBu, 2 ) and {[R₂Sn(m‐CO₂C₆H₄S)R₂Sn(m‐SC₆H₄CO₂)SnR₂]O}₂ (R=Me, 3 ; nBu, 4 )—have been prepared by treatment of o‐ or m‐mercaptobenzoic acid and the corresponding R₂SnCl₂ (R=Me, nBu) with sodium ethoxide in ethanol (95 %). All the complexes were characterized by elemental analysis, FT‐IR and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy, TGA, and X‐ray crystallography diffraction analysis. The molecular structure analyses reveal that both 1 and 2 are hexanuclear macrocycles with hydrophobic “pseudo‐cage” structures, while 3 and 4 are hexanuclear macrocycles with double‐cavity structures. Furthermore, the supramolecular structure analyses show that looser and more intriguing supramolecular infrastructures were also found in complexes 1 – 4 , which exist either as one‐dimensional chains of rings or as two‐dimensional networks assembled from the organometallic subunits through intermolecular C? H???S weak hydrogen bonds (WHBs) and π–π interactions.     

Ion Pairing,H‐bonding,and π‐π Interactions in Cobalt(II) Compound Containing Guanidinium Counter Ion

A novel proton transfer compound, (GH)₂(phendc), ( 1 ), was synthesized from the reaction of 1,10‐phenanthroline‐2,9‐dicarboxylic acid, phendcH₂, and guanidine hydrochloride, (GH)(Cl), (G: guanidine). The characterization was performed using IR, ¹H and ¹³C NMR spectroscopy. The cobalt(II) compounds were synthesized using proton transfer compounds containing guanidinium counter ion. These proton transfer compounds are (GH)₂(phendc), and (GH)₂(pydc) (pydcH₂: 2,6‐pyridinedicarboxylic acid). The chemical formulae and space groups are (GH)₂[Co(phendc)₂]·4H₂O, (2) , and (GH)₂[Co(H₂O)₆][Co(pydc)₂]₂, P2₁/n (3) . Non‐covalent interactions such as ionpairing, hydrogen bonding and π‐π stacking are discussed.     

Synthesis and characterization of novel π‐conjugated polymers with phosphole ring derivatives

Novel π‐conjugated polymers ( 8 – 10 ) were prepared by the palladium‐catalyzed Sonogashira coupling reaction of three kinds of phosphole‐ring‐containing monomers with 2,5‐dihexyloxyl‐1,4‐diethynylbenzene. The obtained polymers ( 8 – 10 ) were regioregulated with the 2,5‐substituted phosphole ring in the polymer main chain and characterized with ¹H, ¹³C, and ³¹P NMR and FTIR. Polymers 8 – 10 were found to have an extended π‐conjugated system according to the results of UV–vis absorption spectra. In the fluorescence emission spectra of 8 – 10 , moderate emission peaks were observed in the visible blue‐to‐green region. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2867–2875, 2007     

Hydrogen bonding and π–π stacking in 6‐hydroxy­biochanin A monohydrate

In the lattice of the title compound (systematic name: 5,6,7‐trihydroxy‐4′‐meth­oxy­isoflavone monohydrate), C₁₆H₁₂O₆·H₂O, the isoflavone mol­ecules are linked into chains through R₄³(17) motifs composed via O—H⋯O and C—H⋯O hydrogen bonds. Centrosymmetric R₄²(14) motifs assemble the chains into sheets. Hydrogen‐bonding and aromatic π–π stacking inter­actions lead to the formation of a three‐dimensional network structure.     

Experimental and quantum chemical calculational studies on N‐[4‐(3‐Methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐N′‐pyridin‐3ylmethylene‐hydrazine

The title molecule, N‐[4‐(3‐Methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐N′‐pyridin‐3ylmethylene‐ hydrazine (C₂₀ H₂₀ N₄ S₁), was characterized by ¹H‐NMR, ¹³C‐NMR, IR, UV‐visible, and X‐ray determination. In addition to the molecular geometry from X‐ray experiment, the molecular geometry, vibrational frequencies and gauge including atomic orbital ¹H‐ and ¹³C‐NMR chemical shift values of the title compound in the ground state have been calculated using the Hartree‐Fock and density functional method (B3LYP) with 6‐31G(d, p) basis set. The calculated results show that optimized geometries can well reproduce the crystal structural parameters. By using time‐dependent density functional theory method, electronic absorption spectrum of the title compound has been predicted. © 2011 Wiley Periodicals, Inc.     

A Molecular Nanotube with Three‐Dimensional π‐Conjugation

A π‐conjugated twelve‐porphyrin tube is synthesized in 32 % yield by a template‐directed coupling reaction that joins together six porphyrin dimers, forming twelve new C? C bonds. The nanotube has two bound templates, enclosing an internal volume of approximately 4.5 nm³. Its UV/Vis/NIR absorption and fluorescence spectra resemble those of a previously reported six‐porphyrin ring, but are red‐shifted by approximately 300 cm^?1, reflecting increased conjugation. Ultrafast fluorescence spectroscopy demonstrates extensive excited‐state delocalization. Transfer of electronic excitation from an initially formed state polarized in the direction of the nanotube axis (z axis) to an excited state polarized in the xy plane occurs within 200 fs, resulting in a negative fluorescence anisotropy on excitation at 742 nm.     

The effects of σC—Se–π hyperconjugation in 1‐methoxy‐ and 1‐nitro‐4‐[(phenylselanyl)methyl]benzene

The structures of 1‐methoxy‐4‐[(phenylselanyl)methyl]benzene, C₁₄H₁₄OSe, (1), and 1‐nitro‐4‐[(phenylselanyl)methyl]benzene, C₁₃H₁₁NO₂Se, (2), were determined at 130 K. The two structures, which differ in that (1) contains an electron‐rich aromatic ring and (2) contains an electron‐deficient aromatic ring, both adopt conformations which allow for σ_C—Se–π hyperconjugation. However, although there are significant differences in the ⁷⁷Se chemical shifts for these two compounds, they do not display significantly different H₂C—Se or H₂C—C_ar bond lengths, suggesting that the effects of σ_C—Se–π hyperconjugation in (1) and (2) are not strong enough to be manifested in measurable differences in the structural parameters.     

Synthesis,Crystal Structure,and Physical Property of Sterically Unprotected Thiophene/Phenylene Co‐Oligomer Radical Cations: A Conductive π–π Bonded Supermolecular meso‐Helix

Sterically unprotected thiophene/phenylene co‐oligomer radical cation salts BPnT^.+[Al(OR_F)₄]^? (OR_F=OC(CF₃)₃, n=1–3) have been successfully synthesized. These newly synthesized salts have been characterized by UV/Vis‐NIR absorption and EPR spectroscopy, and single‐crystal X‐ray diffraction analysis. Their conductivity increases with chain length. The formed meso‐helical stacking by cross‐overlapping radical cations of BP2T^.+ is distinct from previously reported face‐to‐face overlaps of sterically protected (co‐)oligomer radical cations.     

Structures of rhenium(I) complexes with 3‐hydroxyflavone and benzhydroxamic acid as O,O′‐bidentate ligands and confirmation of π‐stacking by solid‐state NMR spectroscopy

The synthesis and crystal structures of two new rhenium(I) complexes obtained utilizing benzhydroxamic acid (BHAH) and 3‐hydroxyflavone (2‐phenylchromen‐4‐one, FlavH) as bidentate ligands, namely tetraethylammonium fac‐(benzhydroxamato‐κ²O,O′)bromidotricarbonylrhenate(I), (C₈H₂₀N)[ReBr(C₇H₆NO₂)(CO)₃], 1 , and fac‐aquatricarbonyl(4‐oxo‐2‐phenylchromen‐3‐olato‐κ²O,O′)rhenium(I)–3‐hydroxyflavone (1/1), [Re(C₁₅H₉O₃)(CO)₃(H₂O)]·C₁₅H₁₀O₃, 3 , are reported. Furthermore, the crystal structure of free 3‐hydroxyflavone, C₁₅H₁₀O₃, 4 , was redetermined at 100 K in order to compare the packing trends and solid‐state NMR spectroscopy with that of the solvate flavone molecule in 3 . The compounds were characterized in solution by ¹H and ¹³C NMR spectroscopy, and in the solid state by ¹³C NMR spectroscopy using the cross‐polarization magic angle spinning (CP/MAS) technique. Compounds 1 and 3 both crystallize in the triclinic space group P with one molecule in the asymmetric unit, while 4 crystallizes in the orthorhombic space group P2₁2₁2₁. Molecules of 1 and 3 generate one‐dimensional chains formed through intermolecular interactions. A comparison of the coordinated 3‐hydroxyflavone ligand with the uncoordinated solvate molecule and free molecule 4 shows that the last two are virtually completely planar due to hydrogen‐bonding interactions, as opposed to the former, which is able to rotate more freely. The differences between the solid‐ and solution‐state ¹³C NMR spectra of 3 and 4 are ascribed to inter‐ and intramolecular interactions. The study also investigated the potential labelling of both bidentate ligands with the corresponding fac‐^99mTc‐tricarbonyl synthon. All attempts were unsuccessful and reasons for this are provided.     

Darstellung von Bis‐(2‐chlorethyl)amino‐substituierten Diazaphosphorinonen. Reversible oxidative Addition von Hexafluoraceton an σ3λ3‐Phosphor‐Verbindungen. Synthese von σ5λ5‐Spirophosphoranen und deren Zersetzung

Synthesis of Bis‐(2‐chloroethyl)amino‐substituted Diazaphosphorinones. Reversible Oxidative Addition of Hexafluoroacetone to σ³λ³‐Phosphorus Compounds. Synthesis of σ⁵λ⁵‐Spirophosphoranes and their Decomposition The reaction of 1‐methyl‐pyrido[3,2‐e]‐3,1‐oxazin‐2,4‐dione ( 1 ) with benzylamines led to the aminonicotinic acid amides 2 – 4 . Their reaction with phosphorus trichloride furnished the P‐chloro‐pyridodiazaphosphorinones 5 – 7 , which, upon reaction with bis‐(2‐chloroethyl) ammonium chloride/triethylamine, were converted into the P‐bis‐(2‐chloroethyl)amino‐substituted pyridodiazaphosphorinones 8 – 10 . The P‐chloro‐benzodiazaphosphorinone 11 was allowed to react with 2‐chloroethylammonium chloride/triethylamine to form the 2‐chloroethylamino‐substituted derivative 12 . The σ³‐diazaphosphorinones 8 , 9 , 12 and 13 were oxidized with the urea‐hydrogen peroxide‐(1 : 1)‐adduct to the corresponding phosphoryl derivatives 14 – 17 . The oxidative addition of hexafluoroacetone (HFA) to the σ³‐diazaphosphorinone 18 led, with abstraction of methyl chloride, to the tricyclic phosphorane 19 b . The spirophosphoranes 21 – 23 were formed by reaction of compounds 8 , 9 and 13 with HFA. NMR‐studies were made on the decomposition of the bicyclic phosphoranes 20 a , 22 and 23 . The oxidative addition of HFA to diazaphosphorinones was found to be reversible. Single crystal X‐ray determinations were conducted on compounds 17 and 19 b . They confirm the expected connectivity. Compound 17 was found to exhibit short C–H‥ O‐hydrogen bonds (H…O 234 pm). Compound 19 crystallises as two independent molecules which differ, e. g., in the orientation of the chloroethyl groups.     

Synthesis, π‐Face‐Selective Aggregation,and π‐Face Chiral Recognition of Configurationally Stable C3‐Symmetric Propeller‐Chiral Molecules with a π‐Core

The C₃‐symmetric propeller‐chiral compounds (P,P,P)‐ 1 and (M,M,M)‐ 1 with planar π‐cores perpendicular to the C₃‐axis were synthesized in optically pure states. (P,P,P)‐ 1 possesses two distinguishable propeller‐chiral π‐faces with rims of different heights named the (P/L)‐face and (P/H)‐face. Each face is configurationally stable because of the rigid structure of the helicenes contained in the π‐core. (P,P,P)‐ 1 formed dimeric aggregates in organic solutions as indicated by the results of ¹H NMR, CD, and UV/Vis spectroscopy and vapor pressure osmometry analyses. The (P/L)/(P/L) interactions were observed in the solid state by single‐crystal X‐ray analysis, and they were also predominant over the (P/H)/(P/H) and (P/L)/(P/H) interactions in solution, as indicated by the results of ¹H and 2D NMR spectroscopy analyses. The dimerization constant was obtained for a racemic mixture, which showed that the heterochiral (P,P,P)‐ 1 /(M,M,M)‐ 1 interactions were much weaker than the homochiral (P,P,P)‐ 1 /(P,P,P)‐ 1 interactions. The results indicated that the propeller‐chiral (P/L)‐face interacts with the (P/L)‐face more strongly than with the (P/H)‐face, (M/L)‐face, and (M/H)‐face. The study showed the π‐face‐selective aggregation and π‐face chiral recognition of the configurationally stable propeller‐chiral molecules.