Conjugated polymer sensors built on pi-extended borasiloxane cages

Control of Bandgaps and Energy Levels in Water-Soluble Discontinuously Conjugated Polymers through Chemical Modification

Bandgap and energy levels are crucial for developing new electronic and photonic devices because photoabsorption is highly dependent on the bandgap. Moreover, the transfer of electrons and holes between different materials depends on their respective bandgaps and energy levels. In this study, we demonstrate the preparation of a series of water-soluble discontinuously π-conjugated polymers through the addition-condensation polymerization of pyrrole (Pyr), 1,2,3-trihydroxybenzene (THB) or 2,6-dihydroxytoluene (DHT), and aldehydes, including benzaldehyde-2-sulfonic acid sodium salt (BS) and 2,4,6-trihydroxybenzaldehyde (THBA). To control the energy levels of the polymers, varying amounts of phenols (THB or DHT) were introduced to alter the electronic properties of the polymer structure. The introduction of THB or DHT into the main chain results in discontinuous conjugation and enables the control of both the energy level and bandgap. Chemical modification (acetoxylation of phenols) of the polymers was employed to further tune the energy levels. The optical and electrochemical properties of the polymers were also investigated. The bandgaps of the polymers were controlled in the range of 0.5-1.95 eV, and their energy levels could also be effectively tuned.

Electrical Conductivities of Narrow-Bandgap Polymers with Two Types of π-Conjugated Post-Crosslinking

Bandgap energy is one of the most important properties for developing electronic devices because of its influence on the electrical conductivity of substances. Many methods have been developed to control bandgap, one of which is the realization of conducting polymers using narrow-bandgap polymers; however, the preparation of these polymers is complex. In this study, water-soluble, narrow-bandgap polymers with reactive groups were prepared by the addition–condensation reaction of pyrrole (Pyr), benzaldehyde-2-sulfonic acid sodium salt (BS), and aldehyde-containing reactive groups (aldehyde and pyridine) for post-crosslinking. Two types of reactions, aldehyde with p-phenylenediamine and pyridine with 1,2-dibromoethylene, were carried out for the π-conjugated post-crosslinking between polymers. The polymers were characterized by proton nuclear magnetic resonance (¹H-NMR), thermogravimetric/differential thermal analysis (TG/DTA), UltraViolet-Visible-Near InfraRed spectroscopy (UV-Vis-NIR), and other analyses. The bandgaps of the polymers, calculated from their absorption, were less than 0.5 eV. Post-crosslinking prevents resolubility and develops electron-conducting routes between the polymer chains for π-conjugated systems. Moreover, the post-crosslinked polymers maintain their narrow bandgaps. The electrical conductivities of the as-prepared polymers were two orders of magnitude higher than those before the crosslinking.

Synthesis and optical properties of N→Ga coordinated gallium boroxines

Reactions of the N,C,N-chelated organogallium amide LGa(NEt₂)₂ (1), where L is {2,6-(Me₂NCH₂)₂C₆H₃}^-, with organoboronic acids RB(OH)₂ yielded molecular gallium boroxines LGa(O₃B₂R₂) (2: R = OH, 3: R = Ph, 4: R = 4-MeO-C₆H₄, 5: R = 4-CHO-C₆H₄, 6: R = Fc), neutral analogues of gallaborates. The molecular structures revealed the presence of a six-membered central GaB₂O₃ ring. The film forming properties of 5 allowed the deposition of transparent thin films by a spin coating method. The thicknesses, refractive index, energy of the optical gap (Eoptg), activation energy of surface electrical conductivity (Esa) and pre-exponential factor (σ₀) of the thin layers of 5 were measured and they are close to those found for related oxygen glass. Finally, GBO 5 was also used as an additive to printing ink and a thin film of 5 was prepared by the gravure printing technique.

Spiropyran based recognitions of amines: UV-Vis spectra and mechanisms

As one of the important photochromic molecules, spiropyran (SP) compounds are widely used as detectors and fluorescence probes in the environment and bio-imaging field. Although great achievements have been attained for various sophisticated spiropyrans in metal ion sensing, less success is achieved in sensing organic molecules due to the weak interaction between the spiropyran and the target of the organic molecule. In this study, a spiropyran derivative containing a hydroxyl group (SPOH) was employed for the recognition of four kinds of amines via ultraviolet-visible (UV-Vis) spectra. The aliphatic primary amines, aromatic primary amines, aliphatic secondary and tertiary amines, aromatic secondary and tertiary amines were successfully distinguished according to the shapes and trends of their UV-Vis absorption spectra. The chemical reaction between aliphatic, aromatic primary amines and SPOH as well as alkalinity are two vital interaction mechanisms for the recognition process which are testified by Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR). Although SP is generally water-insoluble, it is easy to achieve soluble by fixing SPOH inside micelle or vesicle and thus the results in this study is meaningful for amine recognition utility in environments and biological systems.

First example of solid-state luminescent borasiloxane-based chiral helices assembled through N-B bonds

The reaction between differently substituted borasiloxanes and 2,5-bis(3-pyridylethynyl)thiophene provided the first example of luminescent borasiloxane-based chiral helices held together by N-B bonds. The starting building blocks and the helices were fully characterized, and the nature of the N-B bond rationalized by means of theoretical calculations.

Ion specific fluorescence modulation of polyvinyl alcohol-boronate matrices

Borylated polymers are emerging as valuable chemosensors that can report analyte binding through an array of responses. Condensing aryl boronic acids onto polyvinyl alcohol affords fluorescent polymers that can detect and extract borophilic anions.

BN- and BO-Doped Inorganic-Organic Hybrid Polymers with Sulfoximine Core Units

While polysulfones constitute a class of well-established, highly valuable applied materials, knowledge about polymers based on the related sulfoximine group is very limited. We have employed functionalized diaryl sulfoximines and a p-phenylene bisborane as building blocks for unprecedented BN- and BO-doped alternating inorganic-organic hybrid copolymers. While the former were accessed by a facile silicon/boron exchange protocol, the synthesis of polymers with main-chain B-O linkages was achieved by salt elimination.

Second-order nonlinear optical properties of eight-membered centrosymmetric cyclic borasiloxanes

SHG efficiencies of eight-membered centrosymmetric cyclic borasiloxanes arise form distorted silicon atom, strong electron withdrawing group and non-covalent interactions in crystal packing.

Introduction of Boron Functionalities into Silsesquioxanes: Novel Independent Methodologies

Owing to their versatile application possibilities, silsesquioxanes (SQs) are of considerable interest for creating hybrid inorganic-organic materials. In this report, two novel and independent strategies for the direct attachment of boron functionalities to silsesquioxanes are presented. Encouraged by our previous work concerning the synthesis of borasiloxanes through the catalyst-free dehydrogenative coupling of silanols and boranes, we decided to apply our method to a synthesis of various boron-functionalized silsesquioxanes. During our tests, we also investigated the activity of scandium(III) triflate, which we have previously used as an excellent catalyst for the obtaining of Si-O-Si and Si-O-Ge moieties. As a result, we also discovered a novel approach for the O-borylation of Si-OH groups in silsesquioxanes with allylborane. Both routes are highly chemoselective and efficiently lead to the obtaining of Si-O-B moiety under air atmosphere and at room temperature.

Organoboron copolymers containing thienothiophene and selenophenothiophene analogues: optical, electrochemical and fluoride sensing properties

Conjugated D–A copolymers of SeT/TT and mesitylboron were synthesized. Large Stokes shifts of 96–166 nm and solution quantum yields of 5–18% were recorded. High fluoride sensing property was observed for the polymer having cross-conjugated-TT units.

Synthesis of borasiloxanes by oxidative hydrolysis of silanes and pinacolborane using Cu3(BTC)2 as a solid catalyst

This work reports the synthesis of borasiloxanes from silanes and pinacolboranes using Cu₃(BTC)₂ as a heterogeneous catalyst in acetonitrile under mild conditions.

Ruthenium-catalysed multicomponent synthesis of borasiloxanes

Ruthenium-catalysed multicomponent synthesis of borasiloxanes directly from silanes, boranes and water is reported.

A convenient and clean synthetic method for borasiloxanes by Pd-catalysed reaction of silanols with diborons

Pd-Catalysed O-borylation of silanols with diborons selectively proceeded to give the corresponding boryl silyl ethers in high yields.

Eight membered cyclic-borasiloxanes: synthesis, structural, photophysical, steric strain and DFT calculations

A series of eight membered cyclic borasiloxanes were synthesized and structurally characterized. The photophysical properties were investigated. HOMO–LUMO, hyperpolarizability and steric strain were computed by B3LYP/6-31+G** method.

From Stiba- and Bismaheteroboroxines to N,C,N-Chelated Diorganoantimony(III) and Bismuth(III) Cations-An Unexpected Case of Aryl Group Migration

An unprecedented transfer of an aryl group from boron to Sb and Bi is observed in the reaction of heteroboroxines of general formula ArM[(OBR)2O] [where M = Sb, Bi; Ar = C6H3-2,6-(CH2NMe2)2; R = Ph, 4-CF3C6H4, 4-BrC6H4] with corresponding boronic acid RB(OH)2. Using this procedure, ion pairs [ArMR](+)[R4B5O6](-) were obtained [where M = Sb and R = Ph (4), 4-CF3C6H4 (5), 4-BrC6H4 (6); where M = Bi and R = Ph (7), 4-CF3C6H4 (8), 4-BrC6H4 (9)]. All compounds were characterized using elemental analysis, electrospray ionization mass spectrometry, and multinuclear NMR spectroscopy, and molecular structures of 4 and 7 were determined by single-crystal X-ray diffraction analysis. The central metal atoms in 4-9 were arylated by respective boronic acids, which represents, to the best of our knowledge, unprecedented reaction path in the chemistry of heavier group 15 elements. Investigation of the mechanism of this transformation indicated that Lewis pairs consisting of monomeric oxides ArMO and boroxine rings are probably key intermediates. In this regard, molecular structures of ArSbO[(4-CF3C6H4)3B3O3]·(4-CF3C6H4)B(OH)2 (10) and {ArSbO[(3,5-(CF3)2C6H3)3B3O3]} (13) were established by single-crystal X-ray diffraction analysis, and compound 13 was also fully characterized in solution by multinuclear NMR spectroscopy. The bonding in 13 was analyzed in detail by using density functional theory and natural bond order calculations and compared with known adduct ArSbOB(C6F5)3 (14) and hypothetical ArSbO monomer.

Multifaceted strategy for the synthesis of diverse 2,2'-bithiophene derivatives

New catalytically or high pressure activated reactions and routes, including coupling, double bond migration in allylic systems, and various types of cycloaddition and dihydroamination have been used for the synthesis of novel bithiophene derivatives. Thanks to the abovementioned reactions and routes combined with non-catalytic ones, new acetylene, butadiyne, isoxazole, 1,2,3-triazole, pyrrole, benzene, and fluoranthene derivatives with one, two or six bithiophenyl moieties have been obtained. Basic sources of crucial substrates which include bithiophene motif for catalytic reactions were 2,2'-bithiophene, gaseous acetylene and 1,3-butadiyne.

Synthesis, optical, electrochemical properties and photovoltaic performance of novel panchromatic meso-thiophene BODIPY dyes with a variety of electron-donating groups at the 3,5-positions

A series of novel BODIPY derivatives (BDP1–5) containing a thiophene motif at the meso-position and various electron-donating units at the 3,5-positions were designed and synthesized.

Temperature- and voltage-induced ligand rearrangement of a dynamic electroluminescent metallopolymer

A dynamic-covalent metal-containing polymer was synthesized by the condensation of linear diamine and dialdehyde subcomponents around copper(I) templates in the presence of bidentate phosphine ligands. In solution, the red polymers undergo a sol-gel transition upon heating to form a yellow gel, a process that can be either reversible or irreversible depending on the solvent used. When fabricated into a light-emitting electrochemical cell (LEC), the polymer emits infrared light at low voltage. As the voltage is increased, a blue shift in the emission wavelength is observed until yellow light is emitted, a process which is gradually reversed over time upon lowering the voltage. The mechanism underlying these apparently disparate responses is deduced to be due to loss of the copper phosphine complex from the polymer.

Synthesis of heteroboroxines with MB₂O₃ core (M = Sb, Bi, Sn)--an influence of the substitution of parent boronic acids

The synthesis and structure of stiba-, stanna- and bismaheteroboroxines of a general formula L(E)M[(OBR)2O] supported by a N,C,N-chelating ligand L [where L = C6H3-2,6-(CH2NMe2)2, M, E = Sb, lone pair or Sn, Ph or Bi, lone pair] is reported. The target compounds are prepared by straightforward one-step reactions between oxides (LMO)2 (M = Sb or Bi) or organotin(iv) carbonate L(Ph)Sn(CO3) with four or two molar equivalents of corresponding organoboronic acid. All compounds were characterized with the help of elemental analysis, multinuclear NMR spectroscopy and on several occasions the molecular structure was determined using single-crystal X-ray diffraction analysis. The influence of both the substitution of the parent organoboronic acid and the central atom used on the feasibility of the condensation reaction was addressed. Furthermore, several heteroboroxines containing nitrogen donor functionality (i.e. NH2, NMe2, CN or 4-pyridyl) included in the boronic acid residue were synthesized and characterized with the aim to prepare boroxine-based covalent frameworks (through intermolecular N→B interactions) containing metal atoms in their structures. Although no such intermolecular bonding was detected in solution of these compounds, it was shown that the organotin(iv) heteroboroxine substituted by 4-pyridyl group forms an infinite polymeric chains via N→B interactions in the solid state. This polymer collapsed back to monomeric units upon dissolution.

Riboflavin-based fluorogenic sensor for chemo- and enantioselective detection of amine vapors

A novel turn-on fluorogenic chiral sensory system has been developed using a protonated riboflavin and riboflavin-derived cationic polymer as a fluorophore precursor and a specific amine receptor, respectively, which enables the solid-state chemo- and enantioselective fluorogenic visual detection of primary and secondary amine vapors.

Conjugated amplifying polymers for optical sensing applications

Thanks to their unique optical and electrochemical properties, conjugated polymers have attracted considerable attention over the last two decades and resulted in numerous technological innovations. In particular, their implementation in sensing schemes and devices was widely investigated and produced a multitude of sensory systems and transduction mechanisms. Conjugated polymers possess numerous attractive features that make them particularly suitable for a broad variety of sensing tasks. They display sensory signal amplification (compared to their small-molecule counterparts) and their structures can easily be tailored to adjust solubility, absorption/emission wavelengths, energy offsets for excited state electron transfer, and/or for use in solution or in the solid state. This versatility has made conjugated polymers a fluorescence sensory platform of choice in the recent years. In this review, we highlight a variety of conjugated polymer-based sensory mechanisms together with selected examples from the recent literature.

Highly selective fluorescence turn-on chemosensor based on naphthalimide derivatives for detection of copper(II) ions

A new fluorescent probe, DN-SB, was synthesized. DN-SB was based on the naphthalimide derivatives and exhibited high selectivity and sensitivity for Cu(2+) ions. As a Cu(2+)-amplified fluorescent probe, its fluorescence spectrum showed 4.5-fold enhancement in the intensity of the signal at 519 nm on binding with the Cu(2+). Based on the fluorescence titration spectra and job's-plot, binding mode of DN-SB with Cu(2+) was proposed. Fluorescence intensity was linear with concentration of Cu(2+) cation in a range from 4 μM to 7 μM. DN-SB was also sensitive for copper ions. The detection limit was calculated to be 0.15 μM which indicated DN-SB was sensitive to Cu(2+).