Photoinduced electron transfer process on emission spectrum of N,N′-bis(salicylidene)-1,2-phenylenediamine as a Mg2+ cation chemosensor: A first principle DFT and TDDFT study

A Novel Methacryloyl-Masked NIR Fluorescent Probe for Detection of Cysteine and Its Application in Bioimaging

Cysteine (Cys) detection is recognized as an essential element in this investigation due to the critical function of Cys in several physiological processes in living organisms. A new NIR fluorescent probe SNC-Cys has been synthesized by incorporating a five-membered malononitrile derivatized ring as an electron withdrawing group, and a methacryloyl group detection moiety for cysteine. After adding Cys, SNC-Cys shows an emission of 654 nm and further works as a "Turn-on" probe via ICT photomechanism. SNC-Cys has high sensitivity and selectivity for Cys (LOD=0.46 μM) and can discriminate it from other closely related amino acids, molecules with structural similarity, and in some cases very close functional group likeness. Thus, these results allow the effective imaging of Cys in living A549 cells which indicates good cell permeability and high applicability in live cell imaging. This study anticipates that SNC-Cys could be an aid in the detection of Cys-relevant diseases.

Tunable optical properties of isoreticular UiO-67 MOFs for photocatalysis: a theoretical study

A theoretical study of the reported photocatalytic systems based on Zr-based MOF (UiO-67) with biphenyl-4,4'-dicarboxylic acid (bpdc) and 2,2'-bipyridine-5,5'-dicarboxylic acid (bpydc) as linkers was performed. Quantum chemical calculations were carried out to understand the optical properties of the materials and to facilitate the rational design of new UiO-67 derivatives with potentially improved features as photocatalysts under ambient conditions. Hence, the effect of the structural modifications on the optical properties was studied considering different designs based on the nature of the linkers: in 1 only the bpdc linker was considered, or the mixture 1 : 1 between bpdc and bpydc linkers (labeled as 1A). Also, substituents R, -NH2, and -SH, were included in the 1A MOF only over the bpdc linker (labeled as 1A-bpdc-R) and on both bpdc and bpydc linkers (labeled as 1A-R). Thus a family of six isoreticular UiO-67 derivatives was theoretically characterized using Density Functional Theory (DFT) calculations on the ground singlet (S0) and first excited states (singlet and triplet) using Time-Dependent Density Functional Theory (TD-DFT), multiconfigurational post-Hartree-Fock method via Complete Active Space Self-Consistent Field (CASSCF). In addition, the use of periodic DFT calculations suggest that the energy transfer (ET) channel between bpdc and bpydc linkers might generate more luminescence quenching of 1A when compare to 1. Besides, the results suggest that the 1A-R (R: -SH and NH2) can be used under ambient conditions; however, the ET exhibited by 1A, cannot take place in the same magnitude in these systems. These ET can favor the photocatalytic reduction of a potential metal ion, that can coordinate with the bpydc ligand, via LMCT transition. Consequently, the MOF might be photocatalytically active against molecules of interest (such as H2, N2, CO2, among others) with photo-reduced metal ions. These theoretical results serve as a useful tool to guide experimental efforts in the design of new photocatalytic MOF-based systems.

Colorimetric and fluorescence sensing of Zn2+ ion and its bio-imaging applications based on macrocyclic "tet a" derivative

We report on the synthesis and characterization of trans N, N'-di-substituted macrocyclic "tet a" probe (L) for metal ion sensing. Both the colorimetric and fluorescent titration studies are performed with different metal ions. The results have suggested that the probe L is very selective and sensitive towards Zn²⁺ ions with significant changes in color. The pendant armed macrocyclic "tet a" probe has exhibited 1.28× 10⁵ M^-1 binding constant and virtuous selectivity for Zn²⁺ ion than other common metal ions. The detection limit of the probe towards Zn²⁺ ion is 0.027 nM. The selective sensing of Zn²⁺ ion is efficiently reversible with EDTA, which is demonstrated for five cycles without losing sensitivity. The time-resolved single-photon counting (TCSPC) studies have determined the average lifetime value for the probe L and L+ Zn²⁺ ion of 1.29 and 2.96 ns, respectively. The theoretical DFT studies have well supported the experimental outcomes. The practical application of the probe in visualizing intracellular Zn²⁺ ion distribution in live Artemia salina has proved the low cytotoxicity and cell membrane permeability of probe, which makes it capable of sensing Zn²⁺ ion in HeLa cells. Thus, the probe L can act as a selective recognition of Zn²⁺ ion in living cell applications.