Synthesis,Structure, and Reactivity of Diazene Adducts: Isolation of iso‐Diazene Stabilized as a Borane Adduct

This work describes the synthesis and full characterization of a series of GaCl₃ and B(C₆F₅)₃ adducts of diazenes R¹?N?N?R² (R¹=R²=Me₃Si, Ph; R¹=Me₃Si, R²=Ph). Trans‐Ph?N?N?Ph forms a stable adduct with GaCl₃, whereas no adduct, but instead a frustrated Lewis acid–base pair is formed with B(C₆F₅)₃. The cis‐Ph?N?N?Ph ? B(C₆F₅)₃ adduct could only be isolated when UV light was used, which triggers the isomerization from trans‐ to cis‐Ph?N?N?Ph, which provides more space for the bulky borane. Treatment of trans‐Ph?N?N?SiMe₃ with GaCl₃ led to the expected trans‐Ph?N?N?SiMe₃ ? GaCl₃ adduct but the reaction with B(C₆F₅)₃ triggered a 1,2‐Me₃Si shift, which resulted in the formation of a highly labile iso‐diazene, Me₃Si(Ph)N?N; stabilized as a B(C₆F₅)₃ adduct. Trans‐Me₃Si?N?N?SiMe₃ forms a labile cis‐Me₃Si?N?N?SiMe₃ ? B(C₆F₅)₃ adduct, which isomerizes to give the transient iso‐diazene species (Me₃Si)₂N?N ? B(C₆F₅)₃ upon heating. Both iso‐diazene species insert easily into one B?C bond of B(C₆F₅)₃ to afford hydrazinoboranes. All new compounds were fully characterized by means of X‐ray crystallography, vibrational spectroscopy, CHN analysis, and NMR spectroscopy. All compounds were further investigated by DFT and the bonding situation was assessed by natural bond orbital (NBO) analysis.     

Tapered copolymers of styrene and 4-vinylbenzocyclobutene via carbanionic polymerization for crosslinkable polymer films

Well-defined polystyrene homopolymers with surface-adhesive triethoxysilyl end group were synthesized via living carbanionic polymerization, epoxide end-functionalization and subsequent hydrosilylation with triethoxysilane. Grafting-to performance of polymers with various molecular weight (M_n = 3000–14,000 g mol⁻¹) to a silicon surface was examined in dependence of reaction time, polymer concentration, solvent and number of alkoxysilyl end groups. Crosslinkable polymers for surface modification were synthesized by statistical carbanionic copolymerization of 4-vinylbenzocyclobutene (4-VBCB) and styrene, followed by epoxide end-functionalization and triethoxysilane modification (M_n = 4000–14,000 g mol⁻¹). The copolymers were characterized by ¹H-NMR, THF-SEC, and matrix-assisted laser desorption and ionization time-of-flight mass spectrometry. In situ ¹H-NMR kinetic studies in cyclohexane-d₁₂ provided information regarding the monomer gradient in the polymer chains, with styrene being the more reactive monomer (r_s = 2.75, r_4-VBCB = 0.23). Thin polymer films on silicon wafers were prepared by grafting-to surface modification under conditions derived for the polystyrene homopolymer. The traceless, thermally induced crosslinking reaction of the benzocyclobutene units was studied by DSC in bulk as well as in 3–6 nm thick polymer films. Crosslinked films were analyzed by atomic force microscopy, ellipsometry, and nanoindentation, showing smooth polymer films with an increased modulus. © 2019 The Authors. Journal of Polymer Science published by Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 181–192     

2,4-Dimethoxycarbonyl-1,1,3,3-tetrakis(dimethylamino)-1λ5,3λ5-diphosphete

1,1,3,3 - Tetrakis(dimethylamino) - 1λ⁵,3λ⁵ - diphosphete, 1 , reacts with cyanoformic acid methyl ester to form two isomers of the title compound 2 . Properties, NMR, mass, and IR spectra of 2 , as well as the molecular and crystal structure of the E isomer of 2 , are described and discussed.     

Electrochemiluminescence Bioassays with a Water‐Soluble Luminol Derivative Can Outperform Fluorescence Assays

The most efficient and commonly used electrochemiluminescence (ECL) emitters are luminol, [Ru(bpy)₃]²⁺, and derivatives thereof. Luminol stands out due to its low excitation potential, but applications are limited by its insolubility under physiological conditions. The water‐soluble m‐carboxy luminol was synthesized in 15 % yield and exhibited high solubility under physiological conditions and afforded a four‐fold ECL signal increase (vs. luminol). Entrapment in DNA‐tagged liposomes enabled a DNA assay with a detection limit of 3.2 pmol L^?1, which is 150 times lower than the corresponding fluorescence approach. This remarkable sensitivity gain and the low excitation potential establish m‐carboxy luminol as a superior ECL probe with direct relevance to chemiluminescence and enzymatic bioanalytical approaches.     

On the Photophysical Properties of New Luminol Derivatives and their Synthetic Phthalimide Precursors

The photophysical properties of a series of structurally related 4-aminophthalimides and the corresponding 5-aminophthalic hydrazides (luminols) are reported. Absorption, steady-state, and time-resolved fluorescence spectra of luminols exhibited substitution, solvent, and pH dependence. Singlet lifetimes have been determined by time-resolved laser flash spectroscopy. UV spectra in gas phase and DMSO solution were calculated by TD-DFT which revealed the existence of two low-energy excited singlet states with strong pH-sensitivity.