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The preparation, isolation, and identification of dinitro, trinitro, and tetranitro metalloporphyrins bearing nitro groups on pyrrole rings—desirable intermediates that enable fundamental changes in the chemico‐physical properties of the porphyrin core—are studied. All six possible dinitro‐Ni‐TPP isomers are formed; three are isolated as pure substances using column chromatography, while the remaining three are inseparable. All possible trinitro‐Ni‐TPP isomers are prepared and isolated, except for the 2,7,13 isomer. Attempts to synthesize tetranitro‐Ni‐TPP either through direct nitration of metalloporphyrin or via direct condensation of the nitropyrrole building blocks are unsuccessful. The molecular structures are unambiguously identified using 2D NMR experiments. Some experimental observations, though not all, are consistent with quantum chemical calculations performed on the geometry, energy, Fukui indices, dipole moments of nitroporphyrins, and the energy of nitration intermediates. 

Colloidal semiconductor nanocrystals (NCs) have emerged as promising candidates for developing solutionprocessable optical gain media with potential applications in integrated photonic circuits and lasers. However, the deployment of NCs in these technologies has been hindered by the nonradiative Auger recombination of multiexciton states, which shortens the optical gain lifetime and reduces its spectral range. Here, we demonstrate that these limitations can be overcome by using giant colloidal quantum shells (g-QSs), comprising a quantum-confined CdSe shell grown over a large (∼14 nm) CdS bulk core. Such bulk-nanoscale architecture minimizes exciton− exciton interactions, leading to suppressed Auger recombination and one of the broadest gain bandwidths reported for colloidal nanomaterials, spanning energies both above and, remarkably, below the bandgap. Ultrafast transient absorption and photoluminescence measurements demonstrate that the high-energy portion of optical gain arises from states containing more than 15 excitons per particle, while the unusual sub-bandgap gain behavior results from an Auger-assisted radiative recombination, a mechanism that has traditionally been viewed as a loss pathway. Collectively, these results reveal a unique gain regime associated with bulk-nanocrystal hybrid systems, which offers a promising path toward solution-processable light sources. 

Calix[4]pyrroles (CPs) and polyammonium azacrowns (ACs) are well-known receptors for anions. CPs bind anions by directional hydrogen bonds that do not always work well for aqueous analytes. The positive charge in polyammonium ACs allows for a stronger but non-directional anion-ammonium electrostatic attraction but lack selectivity. Bridging the gap between CPs and ACs could increase affinity and potentially preserve the selectivity of anion binding. We have synthesized a flexible calixpyrrole-azacrown near isosteric receptor and incorporated an environmentally sensitive dansyl fluorophore to enable fluorescence measurements. Anion binding was evaluated using NMR and fluorescence titrations. The isosteric receptor shows a strong affinity for aqueous phosphates and phosphonates (Na + salts) in the order HAsO 4 2− > H 2 PO 4 − > H 2 P 2 O 7 2− > glyphosate 2− > AMP − > methylphosphonate − ≫ ADP 2− or ATP 3− but does not bind halides. This is in stark contrast to CP which shows a strong preference for halides over oxyanions. The anion binding by the new receptor was accompanied by analyte-specific changes in fluorescence intensity and spectral width and by a wavelength shift. These parameters were used in qualitative and quantitative sensing of aqueous anions. By applying machine-learning algorithms, such as linear discriminant analysis and support vector machine linear regression, this one sensor can differentiate between 10 different analytes and accurately quantify herbicide glyphosate and methylphosphonate, a product of sarin, soman or cyclosarin hydrolysis. In fact, glyphosate can be quantified even in the presence of competing anions such as orthophosphate (LODs were ≤ 1 μM). 

Three carboxamidequinoline ligands were synthesized and their complexes with Eu 3+ were used for recognition and detection of organic/inorganic phosphates in water. The signal transduction process is based on an “On–Off–On” switch in the fluorescence signal utilizing changes in the intramolecular charge transfer (ICT). The fluorescence emission of ligands is quenched upon exposure to the Eu 3+ (Off signal). Following the addition of the phosphate analytes the ligand–Eu 3+ complex disassembles, which results in the regeneration of the original emission of the ligand (On signal). In general, the Eu 3+ complexes show higher affinity towards adenosine 5′-triphosphate (ATP) and lower affinity to other phosphates, namely adenosine 5′-diphosphate (ADP), adenosine 5′-monophosphate (AMP), pyrophosphate (H 2 P 2 O 7 2− , PPi), and dihydrogenphosphate (H 2 PO 4 − , Pi).