Selective Hg²⁺ Sensing Behaviors of Rhodamine Derivatives with Extended Conjugation Based on Two Successive Ring-Opening Processes

A novel class of rhodamine derivatives with two spirolactam moieties have been synthesized, and their two stereoisomers of <i>cis</i>- and <i>trans</i>-forms have been successfully separated and isolated, as well as structurally characterized by X-ray crystallography. Attributed to the successive ring-openings of two spirolactam moieties, different solution color, electronic absorption and emission responses were exhibited upon addition of various concentrations of mercury­(II) ion. Arising from two successive ring-opening processes in the presence of various concentration of Hg­(II) ion, two reporting states with different spectroscopic properties were suggested, that is, the first state showing pink color (absorption maximum at 496 nm) but no emission, while the second state giving purple color (absorption maximum at 593 nm) and red emission (emission maximum at 620 nm). The mechanism of such different spectroscopic responses was also proposed and has also been supported by computational studies. An extension of the present work to the study of the corresponding chemodosimeters from the compounds with two spirolactam groups has been made, in which a stoichiometric and irreversible Hg­(II)-promoted reaction of thiosemicarbazides was utilized to form 1,3,4-oxadiazoles

Selective Hg²⁺ Sensing Behaviors of Rhodamine Derivatives with Extended Conjugation Based on Two Successive Ring-Opening Processes

A novel class of rhodamine derivatives with two spirolactam moieties have been synthesized, and their two stereoisomers of <i>cis</i>- and <i>trans</i>-forms have been successfully separated and isolated, as well as structurally characterized by X-ray crystallography. Attributed to the successive ring-openings of two spirolactam moieties, different solution color, electronic absorption and emission responses were exhibited upon addition of various concentrations of mercury­(II) ion. Arising from two successive ring-opening processes in the presence of various concentration of Hg­(II) ion, two reporting states with different spectroscopic properties were suggested, that is, the first state showing pink color (absorption maximum at 496 nm) but no emission, while the second state giving purple color (absorption maximum at 593 nm) and red emission (emission maximum at 620 nm). The mechanism of such different spectroscopic responses was also proposed and has also been supported by computational studies. An extension of the present work to the study of the corresponding chemodosimeters from the compounds with two spirolactam groups has been made, in which a stoichiometric and irreversible Hg­(II)-promoted reaction of thiosemicarbazides was utilized to form 1,3,4-oxadiazoles

Selective Hg²⁺ Sensing Behaviors of Rhodamine Derivatives with Extended Conjugation Based on Two Successive Ring-Opening Processes

A novel class of rhodamine derivatives with two spirolactam moieties have been synthesized, and their two stereoisomers of <i>cis</i>- and <i>trans</i>-forms have been successfully separated and isolated, as well as structurally characterized by X-ray crystallography. Attributed to the successive ring-openings of two spirolactam moieties, different solution color, electronic absorption and emission responses were exhibited upon addition of various concentrations of mercury­(II) ion. Arising from two successive ring-opening processes in the presence of various concentration of Hg­(II) ion, two reporting states with different spectroscopic properties were suggested, that is, the first state showing pink color (absorption maximum at 496 nm) but no emission, while the second state giving purple color (absorption maximum at 593 nm) and red emission (emission maximum at 620 nm). The mechanism of such different spectroscopic responses was also proposed and has also been supported by computational studies. An extension of the present work to the study of the corresponding chemodosimeters from the compounds with two spirolactam groups has been made, in which a stoichiometric and irreversible Hg­(II)-promoted reaction of thiosemicarbazides was utilized to form 1,3,4-oxadiazoles

Selective Hg²⁺ Sensing Behaviors of Rhodamine Derivatives with Extended Conjugation Based on Two Successive Ring-Opening Processes

A novel class of rhodamine derivatives with two spirolactam moieties have been synthesized, and their two stereoisomers of <i>cis</i>- and <i>trans</i>-forms have been successfully separated and isolated, as well as structurally characterized by X-ray crystallography. Attributed to the successive ring-openings of two spirolactam moieties, different solution color, electronic absorption and emission responses were exhibited upon addition of various concentrations of mercury­(II) ion. Arising from two successive ring-opening processes in the presence of various concentration of Hg­(II) ion, two reporting states with different spectroscopic properties were suggested, that is, the first state showing pink color (absorption maximum at 496 nm) but no emission, while the second state giving purple color (absorption maximum at 593 nm) and red emission (emission maximum at 620 nm). The mechanism of such different spectroscopic responses was also proposed and has also been supported by computational studies. An extension of the present work to the study of the corresponding chemodosimeters from the compounds with two spirolactam groups has been made, in which a stoichiometric and irreversible Hg­(II)-promoted reaction of thiosemicarbazides was utilized to form 1,3,4-oxadiazoles

Alkynylplatinum(II) Terpyridine System Coupled with Rhodamine Derivative: Interplay of Aggregation, Deaggregation, and Ring-Opening Processes for Ratiometric Luminescence Sensing

The synthesis and characterization of a platinum­(II) terpyridine system tethered with a latent organic dye of rhodamine derivative as colorimetric and luminescent sensory moiety is reported to show selective Hg²⁺ ion sensing behavior. The interplay of aggregation/deaggregation behavior of the alkynylplatinum­(II) terpyridine complex and the ring-opening process of rhodamine derivative was investigated. The spectral change of aggregation near-infrared emission at 800 nm and rhodamine fluorescence at 585 nm provides a possible ratiometric luminescence measurement. Morphological studies from transmission electron microscopy and scanning electron microscopy images showing nanospherical structures confirmed the aggregation in the absence of Hg²⁺ ion

Supramolecular Assembly of Isocyanorhodium(I) Complexes: An Interplay of Rhodium(I)···Rhodium(I) Interactions, Hydrophobic–Hydrophobic Interactions, and Host–Guest Chemistry

A series of tetrakis­(isocyano)­rhodium­(I) complexes with different chain lengths of alkyl substituents has been found to exhibit a strong tendency toward solution state aggregation upon altering the concentration, temperature and solvent composition. Temperature- and solvent-dependent UV–vis absorption studies have been performed, and the data have been analyzed using the aggregation model to elucidate the growth mechanism. The aggregation is found to involve extensive Rh­(I)···Rh­(I) interactions that are synergistically assisted by hydrophobic–hydrophobic interactions to give a rainbow array of solution aggregate colors. It is noted that the presence of three long alkyl substituents is crucial for the observed cooperativity in the aggregation. Molecular assemblies in the form of nanoplates and nanovesicles have been observed in the hexane–dichloromethane solvent mixtures, arising from the different formation mechanisms based on the alkyl chain length of the complexes. Benzo-15-crown-5 moieties have been incorporated for selective potassium ion binding to induce dimer formation and drastic color changes, rendering the system as potential colorimetric and luminescent cation sensors and as building blocks for ion-controlled supramolecular assembly

Supramolecular Assembly of Isocyanorhodium(I) Complexes: An Interplay of Rhodium(I)···Rhodium(I) Interactions, Hydrophobic–Hydrophobic Interactions, and Host–Guest Chemistry

A series of tetrakis­(isocyano)­rhodium­(I) complexes with different chain lengths of alkyl substituents has been found to exhibit a strong tendency toward solution state aggregation upon altering the concentration, temperature and solvent composition. Temperature- and solvent-dependent UV–vis absorption studies have been performed, and the data have been analyzed using the aggregation model to elucidate the growth mechanism. The aggregation is found to involve extensive Rh­(I)···Rh­(I) interactions that are synergistically assisted by hydrophobic–hydrophobic interactions to give a rainbow array of solution aggregate colors. It is noted that the presence of three long alkyl substituents is crucial for the observed cooperativity in the aggregation. Molecular assemblies in the form of nanoplates and nanovesicles have been observed in the hexane–dichloromethane solvent mixtures, arising from the different formation mechanisms based on the alkyl chain length of the complexes. Benzo-15-crown-5 moieties have been incorporated for selective potassium ion binding to induce dimer formation and drastic color changes, rendering the system as potential colorimetric and luminescent cation sensors and as building blocks for ion-controlled supramolecular assembly

Rhodium(I) Complexes of Tridentate <i>N</i>‑Donor Ligands and Their Supramolecular Assembly Studies

New classes of tridentate <i>N</i>-donor rhodium­(I) complexes have been synthesized and demonstrated to exhibit interesting induced self-assembly behavior by variation of external stimuli, as a result of extensive Rh­(I)···Rh­(I) interactions, with the assistance of π–π stacking and hydrophobic–hydrophobic interactions. An isodesmic aggregation mechanism has also been identified in the temperature-dependent process. Upon aggregation in acetone solution, the complex molecules form wire-like nanostructures with their shape dependent on the π-conjugation of the tridentate ligands. On the other hand, crystalline needles of rhodium­(I) complexes obtained from recrystallization have also been shown to exhibit conductivity on the order of 10^–3 S cm^–1

Rhodium(I) Complexes of Tridentate <i>N</i>‑Donor Ligands and Their Supramolecular Assembly Studies

New classes of tridentate <i>N</i>-donor rhodium­(I) complexes have been synthesized and demonstrated to exhibit interesting induced self-assembly behavior by variation of external stimuli, as a result of extensive Rh­(I)···Rh­(I) interactions, with the assistance of π–π stacking and hydrophobic–hydrophobic interactions. An isodesmic aggregation mechanism has also been identified in the temperature-dependent process. Upon aggregation in acetone solution, the complex molecules form wire-like nanostructures with their shape dependent on the π-conjugation of the tridentate ligands. On the other hand, crystalline needles of rhodium­(I) complexes obtained from recrystallization have also been shown to exhibit conductivity on the order of 10^–3 S cm^–1

A Molecular Chameleon with Fluorescein and Rhodamine Spectroscopic Behaviors

A new class of fluorescein/rhodamine hybrids with two spirolactone rings was reported to exhibit dual-output fluorescent behaviors independently. Isolation and characterization for two diastereomers, <i>trans</i>-<b>RhOH</b> and <i>cis</i>-<b>RhOH</b>, have been made and their X-ray crystal structures determined. In a basic environment, the spirolactone ring on the hydroxyl side will be opened to give a fluorescein-like optical output with the lowest absorptions at 485 and 530 nm emission. On the other hand, a rhodamine-like optical output, i.e., 528 nm absorption and 575 nm emission, will be switched on by a H⁺ or a Hg²⁺ ion, attributed to the spirolactone ring opening on the amino side. In a methanol−buffer system with different pH values, the corresponding p<i>K</i>_a values for the hydroxyl and amino groups were determined as 5.7 and 2.3, respectively. Selective Hg²⁺-sensing properties have also been discussed, and log <i>K</i>_s values of about 3.60 and 3.73 were determined. Confocal microscopic images of <i>Caenorhabditis elegans</i> incubated with <b>RhOH</b> were found to show enhanced fluorescent intensity with a Hg²⁺ ion, demonstrating the potential application of <b>RhOH</b> for in vivo biological imaging