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[Display omitted] • Selective copper hydrogel formation using terpyridine ligand L in dilute acidic medium. • Hydrogel is sensitive to S2− and I− ions. • Anion sensing study confirms the sensitivity of the copper complex towards S2− and I− ions with low LOD values. • DFT calculations were studied for non-covalent interactions and anion sensing study. 2,2′:6′,2″-Terpyridines (tpy) are well known for their ability to form a gel in the presence of transition metals. Due to the strong binding affinities towards transition metal ions aided by non-covalent interactions, tpy tends to form hydrogel with more than one metal ion. Interestingly, a simple chloro substituted 2,2′:6′,2″-terpyridine ligand L selectively forms a gel with only Cu(II) ion in a mild acidic medium. The hydrogel has a fibrous structure and is sensitive to S2− and I− anions, which is confirmed by both morphological analysis and rheological study. The copper complex was characterized using a variety of techniques, including HRMS, ESR, FTIR, elemental analysis, and DFT calculations. Further, DFT calculations were used to study the non-covalent interactions within the complex and to understand why the hydrogel responds to specific anions. The free energies of the CuI and CuS precipitate formation were calculated to get an idea of the feasibility of the process. Notably, UV–visible absorption spectroscopic study shows that the copper(II) complex CuCl 2 L selectively detected S2− and I− anions in aqueous acetonitrile with LOD of 2.63 and 2.08 μM, respectively. [ABSTRACT FROM AUTHOR]

A simple fluorescent sensor of zinc‐terpyridine complex of the terpyridine ligand 4′‐(3,4,5‐trimethoxyphenyl)‐2,2′ : 6′,2′′‐terpyridine was prepared and utilized for selective sensing of pyrophosphate anion (PPi) in aqueous medium at physiological pH. The sensor complex showed an excellent selectivity of PPi over various other anions such as Cl−, F−, Br−, I−, CO32−, HCO3−, NO3−, OH−, HPO42−, SO42−, SO32−, S2O32− in water. UV‐Visible and fluorescence spectroscopic method have been used to perform the detection study. The sensor complex showed ∼50 fold enhancement of fluorescence intensity upon addition of PPi and excellent sensitivity with lowest limit of detection (LOD) for the detection of PPi anion was found to be ∼300 nM. [ABSTRACT FROM AUTHOR]

The synthesis and structural characterization of a new trimethylplatinum(IV) iodide complex of 4'‐(4‐methoxyphenyl)‐2,2':6',2''‐terpyridine ligand L, {PtMe3IL} (1) is reported. The X‐ray crystal structure shows that the terpyridine ligand L binds the platinum(IV) metal center in bidentate fashion, which is well supported by the 1H NMR spectrum of 1. The complex 1 upon crystallization with 1,4‐diiodotetrafluorobenzene (DITFB) forms the halogen bonded complex 1a (1·DITFB). The structural investigation shows that 1a exhibits the halogen bonding interaction in which the non‐coordinated pyridyl nitrogen acts as halogen bond acceptors by forming I···N interaction with iodine atom of DITFB. In addition iodine atom of complex 1 also acts as weak halogen bond acceptor. [ABSTRACT FROM AUTHOR]

• Selective Hg(II) triggered hydrogelation of ligand 4′-(pyridin-2-yl)-2,2′:6′,2″-terpyridine L in dilute nitric acid. • Hg(II)-hydrogel showed non-uniform, fibrous, and well-developed cross-linked gel morphology. • Optimized structure of HgCl 2 L. We report the addition of aqueous solution of different divalent transition metal ions M2+ (M = Mn, Fe, Co, Ni, Cu, Zn, Cd, Hg) to a dilute acidic solution of 4′-(pyridin-2-yl)-2,2′:6′,2″-terpyridine (L). An irreversible, translucent, and thixotropic hydrogel was selectively produced in the case of Hg(II). FESEM and HR-TEM images of Hg(II)-hydrogel showed non-uniform, fibrous, and cross-linked gel morphology. Further, the hydrogel was treated with sodium salts of different anions (F−, I−, Br−, Cl− , SO 4 2−, NO 3 −, HCO 3 −, SO 3 2−) in water. The iodide ion showed unusual behavior by forming a yellow precipitate of the hydrogel with a plate-like structure, as observed from FESEM images. DFT study has also been conducted to understand the aggregation behavior in Hg(II) based hydrogel. We also synthesized the mercury complex HgCl 2 L and characterized it by 1H NMR, elemental analysis, and mass spectrometry. Selective hydrogelation behavior of pyridinyl substituted terpyridine ligand 4′-(pyridin-2-yl)-2,2′:6′,2″-terpyridine L in dilute acidic medium in the presence of Hg(II) is reported and analyzed by FESEM and HRTEM techniques. The influence of anions on the gel morphologies have also been explored. In addition, DFT study has also been conducted to explore the possible interaction in mercury induced hydrogel. [Display omitted] [ABSTRACT FROM AUTHOR]

The hydrogelation behavior of 4′-(4-methoxyphenyl)-2,2′:6′,2′'-terpyridine in the presence of Cu(II), Zn(II), Cd(II), and Hg(II) has been reported, and the morphology has been analyzed using FESEM technique. Blue fluorescence exhibited by the Zn(II), Cd(II), and Hg(II) metallogels when exposed to UV light (365 nm). [Display omitted] We reported the hydrogel formation ability of 4′-(4-methoxyphenyl)-2,2′:6′,2′'-terpyridine L with different transition metal ions in a mild acidic medium. Irreversible, thixotropic and translucent hydrogel was achieved in case of divalent Cu2+, Zn2+, Cd2+ and Hg2+ ions. FESEM images of the hydrogels showed that Cu2+ hydrogel exhibited a fibrous network, while Zn2+ based hydrogel comprised a non-uniform fibrous structure. On the other hand, Cd2+ and Hg2+ hydrogels showed unusual flake-like structures. Further, Zn2+, Cd2+ and Hg2+ hydrogels exhibited blue fluorescence upon exposure to UV light (365 nm). [ABSTRACT FROM AUTHOR]

• The synthesis of a cadmium complex CdCl 2 L of 4´-[4-(4-aminophenyl)phenyl]- 2,2′:6′,2"-terpyridine ligand L and characterization by 1H NMR and single-crystal X-ray diffraction study. • CdCl 2 L receptor selectively detects pyrophosphate anion in CH 3 CN-H 2 O (15:1 v / v, 10 mM HEPES) in the vicinity of other anions. • DFT calculation study supported the detection study, as it indicates an exergonic reaction process and formation of a six-membered chelate ring between the Cd2+ ion receptor and PPi enable the receptor to detect PPi with high selectivity. A simple 1:1 cadmium (II) complex CdCl 2 L of 4´-[4-(4-aminophenyl)phenyl]- 2,2′:6′,2"-terpyridine ligand L was synthesized, and structure was established by 1H NMR and single-crystal X-ray diffraction study. The crystal structure revealed that Cd(II) ion in the complex adopted a distorted trigonal bipyramidal geometry, and coordinated to three nitrogen atoms of the terpyridine domain and two chlorine atoms. The complex shows selective detection of pyrophosphate anion (P 2 O 7 4−, PPi) compared to a variety of different anions (HCO 3 −, I −, SO 4 2−, S 2 O 3 2−, Cl−, CH 3 COO−, CO 3 2−, Br−, SO 3 2−, H 2 PO 4 −, HPO 4 2−, F−, NO 3 −) in CH 3 CN-H 2 O solution (15:1 v / v) buffered with HEPES, with the lowest limit of detection (LOD) for PPi ion ∼ 2.4 µM. UV-Visible absorption spectroscopy and colorimetric method were used in the detection study. The DFT calculations provide a plausible explanation for the observed selectivity since the PPi is the sole anion capable of substituting the ligand in the CdCl 2 L complex due to its ability to form a six-membered chelate ring. A simple cadmium (II) complex CdCl 2 L of 4´-[4-(4-aminophenyl)phenyl]-2,2´:6´,2´´-terpyridine ligand L selectively detects pyrophosphate anion (P 2 O 7 4−, PPi) in CH 3 CN-H 2 O (15:1 v / v, 10 mM HEPES) in the vicinity of other anions through UV-Visible spectroscopic study. The PPi anion detection study is well supported by DFT calculations and colorimetric study. [Display omitted] [ABSTRACT FROM AUTHOR]

• Synthesis of mercury complex HgCl 2 L of terpyridine ligand l. • HgCl 2 L characterised with 1HNMR , HRMS, IR, and SC-XRD. • In-situ prepared HgCl 2 L selective detects S2− anion in aqueous CH 3 CN medium. • The LOD value for sulphide detection is 1.01 μM. A novel mercury complex HgCl 2 L of 4′-(4-N,N´-dimethylaminophenyl)-2,2´:6′,2´´-terpyridine ligand L has been synthesized and characterised using 1H NMR, HRMS, FT-IR spectroscopy and CHN analysis. The crystal structure of HgCl 2 L exhibits distorted square pyramidal geometry. Further, the complex HgCl 2 L is utilised for selectively detecting sulphide (S2−) anion with other competitive anions in aqueous acetonitrile (4:1 v/v) medium. UV–visible absorption spectral studies and colorimetric approach confirmed the selectivity of the complex towards S2- and the limit of detection has been determined to be 1.01 μM. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of novel fluorescent 4′-(3,4-diethoxyphenyl)-2,2′:6′,2′'-terpyridine ligand L. • Utilization of in-situ prepared ZnCl 2 L receptor for selective detection of pyrophosphate in water with LOD ∼36 nm. • Real-Time detection of PPi utilizing Spray test on tissue-paper strips with ZnCl 2 L receptor. • Significant cytotoxic activity against MDAMB-231 cells with IC 50 value 53.85 µM. • Excellent antioxidant activity with an antioxidant percentage of 73.75%. A new fluorescent 4′-(3,4-diethoxyphenyl)-2,2′:6′,2′'-terpyridine ligand L and its 1:1 zinc complex ZnCl 2 L have been synthesized, characterized with the help of NMR, Mass spectroscopy, CHN analysis, and DFT study. In-situ prepared non-fluorescent ZnCl 2 L receptor was utilized for selective detection of pyrophosphate anion (P 2 O 7 4-, PPi) in water (10 mM HEPES buffer, pH 7.4) in the vicinity of other competing analytes (10 equivalents of HPO 4 2-, H 2 PO 4 -, CO 3 2–, HCO 3 –, Cl−, OH–, Br−, CH 3 CO 2 –, F−, I-, NO 3 –, SO 4 2-, SO 3 2-, S 2 O 3 2-, N 3 –) by employing UV–Visible spectroscopy and fluorescence "ON–OFF–ON" mechanism. ZnCl 2 L receptor formed a fluorescent 2:1 adduct with PPi in water during its detection at a nanomolar concentration (LOD ∼27.89 nM). The receptor is also successfully employed in low-cost PPi detection through real-time easily accessible paper strip application. Further, ZnCl 2 L exhibited significant cytotoxic activity against MDAMB-231 cells with an IC 50 value of 53.85 µM and excellent antioxidant activity having an antioxidant percentage of 73.75%. [ABSTRACT FROM AUTHOR]