Molecular interaction of oxazine dyes in aqueous solution: Temperature dependent molecular disposition of the aggregates

Temperature dependent molecular interaction of oxazine dyes, viz., brilliant cresyl blue (C.I. Basic dye), cresyl violet (C.I. Basic violet 3) and nile blue (C.I. Basic blue 12) are studied in aqueous media within a concentration range of 5.0 × 10^− 6 M to 8.0 × 10^− 4 M by UV-visible absorption spectroscopy. The effect of temperature on the geometrical structure of the dimer in solution along with the dimerization equilibria is explained in terms of electrostatic and hydrophobic interactions. Modified non-covalent interaction between two monomer molecules in a dimer as a function of temperature affects the extinction coefficient as well as the geometrical disposition of the dimers and this is well manifested in the exciton splitting of the dimer spectra. The angle θ between main oscillators of the two monomer molecules in a dimer increases by 1.94° for brilliant cresyl blue, whereas an increase of 4.32° and 1.73° were observed for cresyl violet and nile blue respectively due to the increase of temperature from 20 °C to 60 °C.     

Dimer Structures and Laccase-Catalyzed Polymerization Mechanism of Laccol in Fresh Rhus Succedanea Lacquer Sap

Laccase-catalyzed polymerization of laccol was promoted by a kneading process, and the molecular weight distribution and drying properties were examined. The laccol dimers were separated and purified by HPLC, and the chemical structures were characterized by IR, GC-MS, and NMR spectroscopy involving two-dimensional NMR measurements. Two sorts of C-C coupling, nuclear-nuclear (C-C) and nuclear-side chain (C-C), were found in the laccol dimer, which differ from the nuclear-side chain (C-O-C) couplings of urushiol and the only nuclear-nuclear (C-C) couplings of thitsiol. Based on these results, the properties of laccol lacquer film and the laccase-catalyzed polymerization mechanism of laccol are discussed.     

Dimer Acceptor Adopting a Flexible Linker for Efficient and Durable Organic Solar Cells

Organic solar cells (OSCs) have advanced rapidly due to the development of new photovoltaic materials. However, the long-term stability of OSCs still poses a severe challenge for their commercial deployment. To address this issue, a dimer acceptor (dT9TBO) with flexible linker is developed for incorporation into small-molecule acceptors to form molecular alloy with enhanced intermolecular packing and suppressed molecular diffusion to stabilize active layer morphology. Consequently, the PM6 : Y6 : dT9TBO-based device displays an improved power conversion efficiency (PCE) of 18.41 % with excellent thermal stability and negligible decay after being aged at 65 °C for 1800 h. Moreover, the PM6 : Y6 : dT9TBO-based flexible OSC also exhibits excellent mechanical durability, maintaining 95 % of its initial PCE after being bended repetitively for 1500 cycles. This work provides a simple and effective way to fine-tune the molecular packing with stabilized morphology to overcome the trade-off between OSC efficiency and stability.     

One chloro-furoeremophilanoid and two new natural dimers from Ligularia atroviolacea

Three new compounds, including one chloro-furoeremophilanoid （1）, one eremophiladiolide （2）, a rare dimer of nor- furoeremophilanoid, ligulatrovine A （3）, and a known furoeremophilanolide （4）, were isolated from Ligularia atroviolacea. The structures of compounds 1-4 were elucidated by spectroscopic methods including 1D and 2D NMR experiments as well as X- ray diffraction study.     

A novel synthetic path to a luminescent,dimeric samarium complex induced by the hydrolysis of methyl pyridine-3-carboxylate

A novel path to lanthanide complexes of aromatic carboxylates controlled by the hydrolysis of the corresponding aromatic carboxylate ester has been discovered. A dimeric samarium complex of pyridine-3-carboxylate (NIC) has been obtained using methyl pyridine-3-carboxylate (MNIC) as the starting ligand. With the hydrolysis of MNIC to NIC in the presence of sodium hydroxide, samarium ions coordinate to HNIC to form [Sm(NIC)₃(H₂O)₂]₂. X-ray analysis reveals the dimeric structure formed through bridging oxygen atoms of carboxylate groups. The complex crystallizes in the monoclinic space group P2₁/c with a?=?9.668(3), b?=?11.807(3), c?=?17.512(5)?Å, β?=?92.361(3)°, V?=?1997.3(10)?ų, D _c?=?1.838?Mg?m^?3, Z?=?2, R ₁?=?0.0225. The complex exhibits strong luminescence.     

Reactions of [η-carboxycyclopentadiene][η-tetraphenylcyclo butadiene] cobalt with alkyl and aryl tin oxides: Synthesis, structural studies and electrochemistry of novel monomeric and dimeric [η-carboxycyclopentadiene][η-tetraphenylcyclobutadiene]cobalt based stannoxanes

Reactions of [η⁵-carboxycyclopentadienyl][η⁴-tetraphenylcyclobutadiene] cobalt, Ph₄C₄CoC₅H₄COOH (1), with (Ph₃Sn)₂O, [(n-Bu)₂SnO]_n and (Ph₂SnO)_n in refluxing toluene resulted in the formation of the monomeric compound Ph₃SnOC(O)C₅H₄CoC₄Ph₄ (2) and dimeric compounds n-Bu₂Sn[OC(O)C₅H₄CoC₄Ph₄]₂ (3) and Ph₂Sn[OC(O)C₅H₄CoC₄Ph₄]₂ (4), respectively. Reactions carried out in the solid state by mechanical grinding also yielded same results. Crystal structure determination and cyclic voltammetric studies of compounds 1, 2, 3 and 4 have been carried out and compared with similar ferrocene carboxylic acid derivatives. The structures and electrochemistry of these compounds are compared with analogous organotin ferrocene carboxylates. The results obtained from the reaction of 1 with alkyl and aryl tin oxides suggest that the formation of stannoxanes assemblies having more than two carboxylate units are not favored indicating that 1 is a highly sterically hindered metallocene carboxylic acid.     

Synthesis of C6-to-C6 and C3-to-C3 diamide linked γ-cyclodextrin dimers

The syntheses of three new diamide-linked γ-cyclodextrin dimers joined by substitution at either a glucopyranose C6^A or C3^A carbon are reported. The syntheses involve the reaction of either C6^A or C3^A amino-substituted γ-cyclodextrin with bis(4-nitrophenyl)succinate to form succinamide linked γ-cyclodextrin dimers or reaction of C6^A azide-substituted γ-cyclodextrin with carbon dioxide to form a urea linked γ-cyclodextrin dimer.     

Synthesis of new di- and triamine diosgenin dimers

In this study, a high yield synthesis of symmetrical steroidal polyamine dimers was achieved by the dimerization of (25R)-3β-acetoxyfurost-5-en-26-al via several di- and triamine linkers under mild conditions. To ensure the dimerization via E-E ring, the hydroxyl group in diosgenin was protected by an acetyl group. The important step is opening the spiroketal moiety using NaCNBH₃/AcOH to furnish the primary alcohol at C-26, followed by oxidation using PCC/CH₂Cl₂ to synthesize the desired aldehyde. Finally, reductive amination with diaminopropane, diaminobutane, diaminohexane, and spermidine using Na(OAc)₃BH as reducing agent, afforded the required four dimers.     

Quantum Phase Diagram of a Frustrated Spin-1/2 Ferro-Antiferromagnetic Normal Ladder

In this work, we consider a frustrated two-leg spin-1/2 ladder composed of Heisenberg ferromagnetic and antiferromagnetic spin-1/2 chains, and nearest spins from different legs interact via Heisenberg type rung exchange interactions that can be either ferromagnetic or antiferromagnetic in nature. The competing exchange interactions in the system lead to five different quantum phases like ferromagnetic, non-collinear ferrimagnetic (NCF), , antiferromagnetic and dimer phases. The  quantum phase diagram is constructed for the Heisenberg spin-1/2 model and the phases are characterized using the correlation functions which are calculated by the density matrix renormalization group method. We also analyze the  stability of phase and calculate the pitch angle in the NCF phase.