One-Pot Synthesis of Vinylogous Cyano Aminoaryls (VinCAs) as Benzenic Fluorophores: Tailoring Diverse Emission Colors for White Light Emitting Materials and Cell Imaging.

Donor-acceptor-based organic small molecules with an electronic push-pull effect can demonstrate intramolecular charge transfer to show interesting photoluminescence properties. This is an essential criterion for designing fluorogenic probes for cell imaging studies and the development of organic light-emitting diodes. Now, to design such optical materials sometimes it is necessary to tune the band gap by controlling the energies of the highest occupied molecular orbital and lowest unoccupied molecular orbital. Typically, the band gaps could be modulated by installing unsaturated handles between electron-rich donors and electron-deficient acceptors. However, these methods are often synthetically and economically challenging due to the involvement of expensive catalysts and difficult reaction setups. In our present study, we show a straightforward, cost-effective method for obtaining a series of donor-acceptor-type Vinylogous Cyano Aminoaryls (VinCAs) with diverse emission colors. Further studies reveal that these VinCAs can serve as effective cell imaging agents, showcasing potential use in chemical biology. Additionally, these molecules could be further used to generate white light emission (WLE), showing their potential utility in advanced lighting technologies.

Strategic Design of Non-d10 Luminescent Metal-Organic Frameworks as Dual-Mode Ultrafast and Selective Sensing Platforms for Aldehydes at the ppb Level.

Utilizing a cautious design of luminescent MOFs of non-d10 divalent transition metals based on two factors (metal nodes in an octahedral geometry to minimize nonradiative energy dissipation and tailored organic chromophores), this work reports {[Ni2(oxdz)2(tpbn)]}n (1), {[Ni2(oxdz)2(tphn)]}n (2), and {[Ni2(oxdz)2(tpon)]}n (3), synthesized at room temperature, varying the spacer length of tpbn/tphn/tpon (four, six, and eight CH2 groups, respectively). This subtle change in 1-3 is correlated to their hydrophobicity and polarizing power via water vapor sorption and selective and sensitive detection of aldehydes at the ppb level, respectively. A decrease in water vapor uptake (14.8, 8.95, and 3.19 mmol g-1 for 1-3, respectively) is observed with an increase in their hydrophobicity. On the other hand, the solution phase detection limits of acetaldehyde and benzaldehyde (2.42 and 6.71 ppb for 1, 2.77 and 4.08 ppb for 2, and 10.35 and 10.4 ppb for 3, respectively) show a similar trend for their polarizing power. The best performance of 1 is expanded to the vapor-phase detection of acetaldehyde (297% luminescence enhancement) under different pH conditions. The second mode of detection of acetaldehyde via the metal-centered electrochemical behavior of 1 provides detection limits of 38.2 and 71.5 ppb at pH 7 and 13, respectively.

Strategic design of a rare trigonal symmetric luminescent covalent organic framework by linker modification.

We designed a trigonal symmetric imine-linked covalent organic framework (COF), TFPC-DAB, with control over the angularity of the building units, where a bent C2-symmetric diamine, such as 1,3-diaminobenzene (1,3-DAB or DAB), with an exo-angle of 120° was used instead of those with an exo-angle of 180°, in combination with a C3-symmetric trialdehyde, such as tri(4-formylphenoxy)cyanurate (TFPC). Its synthesis was accomplished by reacting the building units in a mixture of mesitylene/dioxane/6 M acetic acid under solvothermal conditions. The phase purity, thermal stability, and porosity of TFPC-DAB were established by various analytical techniques. Utilizing the Density Functional Tight Binding (DFTB+) simulation and Pawley refinement, the best fit of the small angle x-ray pattern was found to have an AA stacking of TFPC-DAB in the trigonal space group P3 with low refinement parameters. Such smart materials are in huge demand to detect hazardous corrosive chemicals, such as HCl and NH3. The dual features of electron deficient π-acidic triazine moiety and heteroatoms (N/O) from TFPC and electron rich phenyl units from DAB embodied in the framework enhance its luminescent property and thereby make it suitable for solvent-based HCl and NH3 sensing. The detection limits for HCl and NH3 in methanol were found to be 14 and 82 ppb, respectively. The effect of solvent polarity on the sensing studies was observed with much lower detection limits in dioxane: 2.5 and 11 ppb for HCl and NH3, respectively. A detailed theoretical calculation using density functional theory and configurational bias Monte Carlo modules was conducted for understanding interactions between the COF and HCl or NH3 analytes.

Synthesis of modified bile acids via palladium-catalyzed C(sp3)-H (hetero)arylation.

A Pd(II)-catalyzed strategy for the diastereo- and regioselective (hetero)arylation of unactivated C(sp3)-H bonds in bile acids is accomplished with aryl and heteroaryl iodides under solvent-free conditions using the 8-aminoquinoline auxiliary as a directing group. This methodology demonstrated excellent functional group tolerance with respect to aryl/heteroaryl iodides on O-protected N-(quinolin-8-yl)cholyl/deoxycholyl amides to afford ß-C(sp3)-H (hetero)arylated products in good-to-excellent yields. Moreover, the 8-aminoquinoline (AQ) auxiliary can easily be removed to obtain modified bile acids.

A convenient route to a vinylogous dicyano aryl based AIEgen with switchable mechanochromic luminescence properties.

Molecules with solid state luminescence and mechanochromic luminescence properties have attracted immense interest owing to their potential application in the areas of organic field-effect transistors (OFETs), organic light-emitting diodes (OLEDs), optoelectronic devices, fluorescence switches, mechano-sensors and data storage. Herein we report a convenient two step synthetic protocol to obtain a couple of luminescent molecules. Using these, a comparative study has been performed to showcase the importance of the weak π⋯π interactions to observe the aggregation induced emission (AIE) and solid-state mechanochromic luminescence. The most fascinating part of this report is to observe the switchable fluorescent dark and bright states of the solid AIEgen. We have also demonstrated the use of the AIEgen to detect volatile organic compounds.

Exploiting a Multi-Responsive Oxadiazole Moiety in One Three-Dimensional Metal-Organic Framework for Remedies to Three Environmental Issues.

Multifunctional metal-organic frameworks (MOFs) rely on the properties of metal centers (nodes) and/or linkers (struts) for their diverse applications in the emerging field of research. Currently, there is a huge demand for MOF materials in the field of capture/fixation/sensing of air pollutants, harmful chemical effluents, and nuclear waste. However, it is a challenging task to utilize one MOF for providing remedies to all these issues. On the basis of our current research activities, we have identified that an oxadiazole moiety-a five-membered ring with two different heteroatoms (O and N)-in a carboxylate linker can be the key to generating such MOF materials for its (a) inherent polarizable nature and molecular docking ability and (b) photoluminescence properties. In this work, we report a 3D MOF {[Co2(oxdz)2(tpbn)(H2O)2]·4H2O}n (1), self-assembled at room temperature from a three-component reaction, with an oxadiazole moiety (where H2oxdz = 4,4'-(1,3,4-oxadiazole-2,5-diyl)dibenzoic acid and tpbn = N,N',N,"N″'-tetrakis(2-pyridylmethyl)-1,4-diaminobutane). The inherent polarizable nature of the oxadiazole moiety in 1 has been efficiently exploited for (i) multimedia iodine capture and (ii) fixation of CO2 under solvent-free and ambient conditions. On the other hand, the luminescent nature of the framework is found to be an efficient, highly preferred turn-on sensor for the ultra-fast detection of ketones with a limit as low as parts-per-trillion (mesitylene oxide: 447 ppt; cycloheptanone: 4.7 ppb; cyclohexanone: 17.2 ppb; acetylacetone: 18 ppb).

Two pillared-layer metal-organic frameworks based on the pinwheel trinuclear carboxylate-clusters of Zn(II) and Co(II): synthesis, crystal structures, magnetic study, and Lewis acid catalysis.

Using a dicarboxylic acid, [1,1'-biphenyl]-4,4'-dicarboxylic acid (H2L1) and an exobidentate ligand, (1E,1'E)-N,N'-(1,4-phenylene)bis(1-(pyridin-4-yl)methanimine) (L2), two 3D interpenetrated networks, {[Zn3(L1)3(L2)]·9H2O}n (Zn-MOF) and {[Co3(L1)3(L2)(DMF)]·0.5DMF}n (Co-MOF), have been prepared in good yields. The crystal structure analysis of Zn-MOF and Co-MOF revealed that both have a 3D pillared-layer structure based on pinwheel trinuclear metal-carboxylate clusters as secondary building units (SBUs). Furthermore, the structures also exhibited three-fold interpenetration. Although the overall networks in Zn-MOF and Co-MOF showed significant resemblances, there are marked differences in their crystal structures, which are associated with the coordination environment of the metal centre and the binding modes of the carboxylates. Gas adsorption studies (N2 at 77 K and 1 bar) indicated that Co-MOF is more porous than Zn-MOF. Magnetic measurements on Co-MOF indicate a significant antiferromagnetic interaction (45 K to 303 K) between trimeric Co(II) S = 3/2 spins through syn-syn carboxylato bridges. Both MOFs were studied for the Lewis acid catalyzed Knoevenagel condensation reactions between benzaldehydes and malononitrile with an active methylene group, where Zn-MOF was found to be a better catalyst than Co-MOF. This was supported by the Monte Carlo simulations indicating the better substrate binding ability of Zn-MOF than Co-MOF.

Tandem Transformation of Indazolones to Quinazolinones through Pd-Catalyzed Carbene Insertion into an N-N Bond.

Serendipitous and expedite transformation of 1-aryl- and 2-aryl-1,2-dihydro-3H-indazol-3-ones to 1,2-di(hetero)aryl- and 2,3-di(hetero)aryl-2,3-dihydroquinazolin-4(1H)-ones, respectively, was achieved in high efficiency by reacting them with aldehydic N-tosylhydrazones. The protocol proceeded through a cascade process involving base-mediated Pd-carbenoid generation by the decomposition of N-tosylhydrazones, nucleophilic attack of indazolone on the Pd-carbenoid complex, and intramolecular ring expansion via N-N bond cleavage. The utility of the strategy is demonstrated toward the synthesis of bioactive NPS 53574, a calcium receptor antagonist.