Pyridine Bridging Research Articles

Assembly of Copper Alkynyl Clusters into Dimensionally Diverse Coordinated Polymers Mediated by Pyridine Ligands.

Surface ligands play crucial roles in modifying the properties of metal nanoclusters and stabilizing atomically precise structures, and also serve as vital linkers for constructing cluster-based coordination polymers. In this study, we present the results of the solvothermal synthesis of eight novel copper alkynyl clusters incorporating pyridine ligands using a one-pot method. The resulting compounds underwent characterization through elemental analysis, Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction (SCXRD). Our observations revealed that distinct pyridine ligands with varying lengths and coordination sites exert significant influence on the structure and dimensionality of the clusters. The structural diversity of these clusters led to the formation of one-dimensional (1D), two-dimensional (2D), or dimer arrangements linked by seven pyridine bridging ligands. Remarkably, these complexes exhibited unique UV-vis absorption and photoluminescence properties, which were influenced by the specific bridging ligand and structural framework. Furthermore, density functional theory (DFT) calculations demonstrated the capability of the conjugated system in the pyridine ligand to impact the band gap of clusters. This study not only unveils the inherent structural diversity in coordination polymers based on copper alkynyl clusters but also offers valuable insights into harnessing ligand engineering for structural and property modulation.

Exploring Efficient Blue Thermally Activated Delayed Fluorescence Emitters by Constructing Intramolecular Hydrogen Bonds

AbstractEfficient blue organic luminescent materials are highly desired for full‐color displays and white lighting based on the organic light‐emitting diode (OLED) technique, but the exploration of robust blue emitters remains challenging. In this work, a series of efficient blue thermally activated delayed fluorescence materials comprised of a benzonitrile acceptor, pyridine bridge, and carbazole‐based donors is designed and synthesized. Intramolecular hydrogen bonds are formed in these molecules, which improve molecular planarity and rigidity. These molecules exhibit excellent thermal stability, high photoluminescence quantum yields, and large horizontal dipole ratios. Highly efficient non‐doped and doped OLEDs are fabricated using these molecules as emitters, providing deep‐blue to sky‐blue lights with outstanding maximum external quantum efficiencies and good operational device lifetime. These results indicate that building intramolecular hydrogen bonds can be an effective strategy for the construction of efficient and robust blue emitters for OLED applications.

Salt of Organosilicon Framework as a Novel Emulsifier for Various Water–Oil Biphasic Systems and a Catalyst for Dibromination of Olefins in an Aqueous Medium

Pickering emulsifiers are significant for organic reactions in an aqueous medium because they have the ability of emulsifying water-oil biphasic systems. For this reason, 2,5-bis[(E)-2-(triethoxysilyl)vinyl]pyridine [BTOSVP] containing a pyridine bridging group was selected as a precursor to prepare a novel salt of organosilicon framework (SOF), an amphiphilic mesoporous pyridine hydrobromide nanosphere. We first synthesized a mesoporous organosilicon framework made up of organic groups containing vinyl groups, pyridine groups, and so forth. Then, hydrobromic acid was added to protonate the pyridine groups in the mesoporous organosilicon framework. Eventually, pyridine hydrobromide salt was formed on the surfaces of channels, and the SOF was successfully prepared for the first time. Pyridine hydrobromide salt can be ionized in water into protonated pyridine cations located on the SOF surfaces and free Br-anions swimming around the protonated pyridine cations because of the electrostatic interaction. In the water-oil biphasic systems, hydrophilicity of SOF originates from the protonated pyridine cations and the lipophilicity of SOF comes from organic groups in the framework; thus, this new kind of SOF can be used as a new generation of solid Pickering emulsifiers. Most importantly, the mesoporous SOF nanosphere can also be used as a catalyst for significantly improved dibromination of olefins in an aqueous medium.

Investigation of Luminescent Triplet States in Tetranuclear CuI Complexes: Thermochromism and Structural Characterization.

To develop new and flexible CuI containing luminescent substances, we extend our previous investigations on two metal‐centered species to four metal‐centered complexes. These complexes could be a basis for designing new organic light‐emitting diode (OLED) relevant species. Both the synthesis and in‐depth spectroscopic analysis, combined with high‐level theoretical calculations are presented on a series of tetranuclear CuI complexes with a halide containing Cu4X4 core (X=iodide, bromide or chloride) and two 2‐(diphenylphosphino)pyridine bridging ligands with a methyl group in para (4‐Me) or ortho (6‐Me) position of the pyridine ring. The structure of the electronic ground state is characterized by X‐ray diffraction, NMR, and IR spectroscopy with the support of theoretical calculations. In contrast to the para system, the complexes with ortho‐substituted bridging ligands show a remarkable and reversible temperature‐dependent dual phosphorescence. Here, we combine for the first time the luminescence thermochromism with time‐resolved FTIR spectroscopy. Thus, we receive experimental data on the structures of the two triplet states involved in the luminescence thermochromism. The transient IR spectra of the underlying triplet metal/halide‐to‐ligand charge transfer (3 m/XLCT) and cluster‐centered (3CC) states were obtained and interpreted by comparison with calculated vibrational spectra. The systematic and significant dependence of the bridging halides was analyzed.

New Pyridine-Bridged Ferrocene-Rhodamine Receptor for the Multifeature Detection of Hg2+ in Water and Living Cells.

A challenge in the design of optical and redox-active receptors is how to combine a specific recognition center with an efficient responsive system to facilely achieve multifeature detection in biological and environmental analyses. Herein, a novel ferrocene–rhodamine receptor conjugated with a pyridine bridge was designed and synthesized. This receptor can sensitively sense Hg2+ in aqueous media via chromogenic, fluorogenic, and electrochemical multisignal outputs with a low detection limit and fast response time. Moreover, it can be qualified as a fluorescent probe for effectively monitoring Hg2+ in living cells. A plausible recognition mode was proposed and rationalized with theoretical calculations.

Redox-Induced Structural Switching through Sporadic Pyridine-Bridged CoIICoII Dimer and Electrocatalytic Proton Reduction.

The homodinuclear CoII helicate complex [CoII(DQPD)]2 (1) was prepared by treating [Co(H2O)6](ClO4)2 with the deprotonated form of the ligand N2,N6-bis(quinolin-8-yl)pyridine-2,6-dicarboxamide (DQPDH2). Complex 1 represents a discrete homodinuclear helicate complex with two CoII centers having a distorted-octahedral geometry through an unprecedented pyridine bridge. Complex 1, upon treatment with H2O2, undergoes oxidation at one of the CoII centers followed by a structural deformation to generate the mixed-valence complex [CoIIICoII(DQPD)2](ClO4) (2·ClO4). In complex 2, the bridging through the central pyridine collapses along with the formation of Co(III) octahedral and Co(II) tetrahedral environments. Complexes 1 and 2 interconvert to one another. The effective magnetic moments for complexes 1 and 2 are respectively 5.88 and 4.30 μB. Complexes 1 and 2 have been employed for electrocatalytic proton reduction using AcOH as the proton source in 95/5 (v/v) DMF/H2O. A TOF of 30000 mmol of H2 h-1 (mol of 1)-1 at a potential of -1.7 V vs SCE was achieved. A resting-state analysis has been carried out to support the mechanism for the catalytic proton reduction.

Pyridine Bridging Diphenylamine-Carbazole with Linking Topology as Rational Hole Transporter for Perovskite Solar Cells Fabrication.

Developing cost-effective and rational hole transporting materials is critical for fabricating high-performance perovskite solar cells (PSCs) and to promote their commercial endeavor. We have designed and developed pyridine (core) bridging diphenylamine-substituted carbazole (arm) small molecules, named as 2,6PyDANCBZ and 3,5PyDANCBZ. The linking topology of core and arm on their photophysical, thermal, semiconducting, and photovoltaic properties were probed systematically. We found that the 2,6PyDANCBZ shows higher mobility and conductivity along with uniform film-forming ability as compared to 3,5PyDANCBZ. The PSCs fabricated with 2,6PyDANCBZ supersede the performance delivered by Spiro-OMeTAD and importantly also gave improved long-term stability. Our findings put forward small molecules based on core-arm linking topology for cost-effective hole selective layers designing.

Soluble Polybenzimidazoles for PEM: Synthesized from Efficient, Inexpensive, Readily Accessible Alternative Tetraamine Monomer

Tetraamine 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine (Py-TAB) was found to be an efficient, readily accessible, inexpensive monomer for synthesizing pyridine bridge polybenzimidazoles (Py-PBIs). The Py-TAB monomer replaced the frequently and conventionally used 3,3′,4,4′-tetraaminobiphenyl (TAB) monomer for synthesizing polybenzimidazoles (PBIs) structure. Py-TAB monomer showed wider scope for synthesis of PBIs with various dicarboxylic acids. Py-PBIs displayed superior solubility in low boiling solvent and hence eliminated the processability issues of PBIs which often restricted the large scale use. Comparable and in some instances superior thermal, mechanical and oxidative stability of Py-PBI proved that the Py-TAB is the most attractive alternative tetraamine monomer to TAB for synthesis of PBIs. The membranes obtained from Py-PBIs displayed significantly lower water uptake and swelling than the conventional PBIs due to the presence of bulky Py-TAB monomer. The presence of pyridine moiety in Py-PBI...

Synthesis and radical coupling of pyridine-bridged π-extended tetrathiafulvalene (TTF)-type donors and push–pull analogues

A new family of pi-extended TTF analogues (3a-c) and D-pi-A chromophores (5a-c), in which the electroactive units (1,3-dithiole rings and 2,2-dicyanovinyl groups) are connected through a pyridine bridge with a meta substitution pattern, is reported. The redox behavior of these compounds has been investigated by cyclic voltammetry and theoretical calculations performed at the B3P86/6-31G** level. Unlike many pi-extended TTF derivatives, the 1,3-dithiole rings in compounds 3a-c do not behave independently and two oxidation processes are observed with an anodic separation ranging from 50 to 150 mV. Calculations show that electrons are equally extracted from both dithiole rings. A biradical structure is predicted for the dication state due to the near-degeneracy of the HOMO and HOMO - 1 orbitals. The presence of both donor (D) and acceptor (A) fragments in conjugates results in irreversible oxidation and reduction processes associated with the 1,3-dithiole ring and with the 2,2-dicyanovinyl moiety, respectively. An electrochemical-chemical-electrochemical (ECE) process takes place for all the compounds reported. The chemical process implies the dimerization of the radical cation for compounds 5 and the oligomerization of the biradical dication for compounds 3. The ECE process therefore generates new neutral dimeric (5) or oligomeric (3) species that incorporate the TTF vinylogue core.

Proton-controlled photoisomerization: rhenium(i) tricarbonyl bipyridine linked to amine or azacrown ether groups by a styryl pyridine bridging ligand

Complexes in which fac-(bpy)Re(CO)3 is linked by a styryl pyridine to an amine or an azacrown ether show no photoreaction in acetonitrile in the absence of acid, but they photoisomerize readily at the stilbene-like bridging ligand when the terminal amine or azacrown ether group is protonated because an intramolecular energy-transfer mechanism becomes available.

Synthesis and Structures of Novel Pyridine-Bridged Phanes of 4,4′-Bipyridine

Syntheses of nine novel phanes derived from 4,4′-bipyridine incorporating new spacer elements are described together with their structural and spectroscopic properties. Starting from the previously unknown pyridine-bridged bis(4,4′-bipyridinium) dication 2 and various bis(bromomethyl)arenes, macrocycles 3–7 were prepared in a simple heterogeneous liquid-liquid reaction in satisfactory yields. In complementary experiments starting from bis(4,4′-bipyridinium) compounds 12–14 with substituted xylenes as spacers, ring closure was performed with 2,6-bis(bromomethyl)pyridine (1) to furnish compounds 16–18 in low yield. Temperature-dependent NMR-spectroscopic studies of the macrocycles were performed to investigate their conformational behaviour. The X-ray crystal structures for phanes 3,4 and 6 illustrate the preferred anti conformation of the macrocycles in the solid state. Consecutive reactions at the pyridine bridge were not successful; however, anisolophane 7 was converted into nitroanisolophane 11 by simple nitration of the anisolo spacer in excellent yield.

Synthesis and Structures of Novel Pyridine-Bridged Phanes of 4,4′-Bipyridine

Syntheses of nine novel phanes derived from 4,4′-bipyridine incorporating new spacer elements are described together with their structural and spectroscopic properties. Starting from the previously unknown pyridine-bridged bis(4,4′-bipyridinium) dication 2 and various bis(bromomethyl)arenes, macrocycles 3–7 were prepared in a simple heterogeneous liquid-liquid reaction in satisfactory yields. In complementary experiments starting from bis(4,4′-bipyridinium) compounds 12–14 with substituted xylenes as spacers, ring closure was performed with 2,6-bis(bromomethyl)pyridine (1) to furnish compounds 16–18 in low yield. Temperature-dependent NMR-spectroscopic studies of the macrocycles were performed to investigate their conformational behaviour. The X-ray crystal structures for phanes 3,4 and 6 illustrate the preferred anti conformation of the macrocycles in the solid state. Consecutive reactions at the pyridine bridge were not successful; however, anisolophane 7 was converted into nitroanisolophane 11 by simple nitration of the anisolo spacer in excellent yield.

The Synthesis and Characterization of a Pyridine-Linked Cyclodextrin Dimer

A cyclodextrin dimer has been synthesized in an overall 29% yield from β-cyclodextrin. This compound contains a pyridine bridge that links the secondary faces of two cyclodextrin units. A complete 1 H and 13 C NMR analysis was performed using a combination of one- and two-dimensional NMR pulse sequences. The results are consistent with the notion that each β-cyclodextrin moiety contains seven spectrally unique sugar resi- dues. In addition, an analysis of key coupling constants suggest that the modified sugar moiety in the individual cyclodextrin units has un- dergone a chair inversion. This analysis represents the first complete NMR characterization of a cyclodextrin dimer

Steric effects of the 2-(diphenylphosphino)pyridine bridging ligand in the synthesis of binuclear palladium( II) complexes

Treatment of [Pd{CH 2C(CH 3)CH 2}(Ph 2PPy)Cl] (Ph 2PPy = 2-(diphenylphosphino)pyridine) with cis-[Pd( tBuNC) 2Cl 2] in dichloromethane affords the mixed isocyanide-tertiary phosphine complex cis-[Pd( tBuNC)Ph 2PPy)Cl 2], in which the Ph 2PPy is a monodentate P-donor, and [{Pd[CH 2C(CH 3)CH 2]Cl} 2]. The steric effects of the Ph 2PPy bridging ligand in determining the reaction course is discussed. The complex cis-[Pd( tBuNC)(Ph 2PPy)Cl 2] was crystallographically characterized: P2 1/ n, a = 15.143(2), b = 9.527(1), c = 17.517(4) Å, β = 113.96(1)°, V= 2309.4(7) Å 3, Z = 4. The final R value was 0.044, R w = 0.046 for the 3078 reflections with I > 3σ( I).

Synthesis of a doubly-bridged oxygen-carrier which shows reduced affinity for carbon monoxide

The synthesis is described of an FeII porphyrin carrying an anthracene bridge across one face and a pyridine bridge across the other; this molecule minics the structural features and properties of natural oxygen-carrying systems.

ChemInform Abstract: PENTAGONAL BIPYRAMIDAL COMPLEXES OF COBALT(II) AND ZINC(II), THE X‐RAY CRYSTAL STRUCTURE OF THE NOVEL DEPROTONATED ZINC DIMER

AbstractKobalt(II)‐chlorid‐hexahydrat (I) bildet mit dem Diacetylpyridin‐bis‐(py?dylhydrazon) (II) den Komplex (III).

Pentagonal bipyramidal complexes of cobalt(II) and zinc(II). The X-ray crystal structure of the novel deprotonated zinc dimer

Pentagonal bipyramidal complexes of cobalt (II) and zinc(II) with 2,6-diacetylpyridine bis-2-pyridyl-hydrazone have been prepared and the zinc complex has been shown to dimerize to an octahedral complex after deprotonation of the ligand, utilizing a pyridine bridge; the structures of the complexes have been determined by X-ray crystallography.

Electron Transfer by Remote Attack in Substituted Pyridine Bridging Ligands

Electron Transfer by Remote Attack in Substituted Pyridine Bridging Ligands