Bromide ions are present in many environments, such as sedative drugs, methyl-bromide-treated vegetables and seawater. Excess bromide in humans interferes with iodide metabolism and is considered toxic. The need for fast and inexpensive methods for bromide detection is of interest. Spectrophotometric detection methods provide accurate and sensitive results. The well-known ability of metalloporphyrins to bind anionic ligands to the central metal ion has been exploited. The changes in the optical properties of Pt(II) 5,10,15,20-tetra(4-methoxy-phenyl)-porphyrin (PtTMeOPP) under the influence of bromide ions allowed us to achieve a fast, simple and reliable UV-vis spectrophotometric method of detection with a detection limit of 2.5 × 10⁻⁸ M and a good confidence coefficient: 99.05%. The potential interfering ions, such as Cl⁻, I⁻, NO₂⁻, NO₃⁻, SCN⁻, SO₃²⁻, SO₄²⁻ and PO₄³⁻ of 100-fold higher and Cl⁻ and R-S⁻ of 1000-fold higher concentrations in the mixture as compared to the determined concentration of bromide ions (c = 10⁻⁵ M), were tested and did not influence the results. The behavior of the sensitive porphyrin in various pH media was investigated in order to determine their influence upon the bromide detection capacity.

A paramagnetic A₃B-type Mn(III)-porphyrin was synthesized and characterized by physical–chemical methods (UV-Vis, FT-IR, ¹H-NMR spectroscopy). The obtained compound was tested as a sensitive material for the spectrophotometric and potentiometric detection of iodine species. Using UV-Vis spectroscopy, the triiodide anions could be detected with high precision in the concentration interval of 1.02 × 10⁻⁵ to 2.3 × 10⁻⁵ M, with an LOD of 9.44 × 10⁻⁶ M. The PVC-based electrode using DOP as a plasticizer showed a sensitivity toward iodide in a wide concentration range of 1.0 × 10⁻⁵ to 1.0 × 10⁻¹ M, with an LOD of 8.0 × 10⁻⁶ M. Both methods are simple, low-cost, and efficient for the detection of iodine species in synthetic samples and pharmaceuticals.

A new sensing material, Pt(II)-5-(4-carboxyphenyl)-10,15,20-tris(4-phenoxyphenyl)-porphyrin (Pt(II)-COOH-TPOPP), was synthesized and characterized. Polymeric membranes containing the porphyrin and three different plasticizers were used as an electroactive material for a new anion-selective sensor. The best composition of the membrane was the one plasticized with dioctylsebacate (DOS), the obtained sensor being citrate-selective in a linear range of 5 × 10⁻⁷–1 × 10⁻¹ M citrate. The slope was Nernstian (19.73 mV/decade) with good selectivity towards a number of interfering anions and a lifetime of five weeks.

The multifunctionality of an A₃B mixed-substituted porphyrin, namely 5-(4-carboxyphenyl)-10,15,20-tris(4-methylphenyl)porphyrin (5-COOH-3MPP), was proven due to its capacity to detect procaine by different methods, depending on the polymer matrix in which it is incorporated. The hybrid nanomaterial containing k-carrageenan and AuNPs (5-COOH-3MPP-k-carrageenan-AuNPs) was able to optically detect procaine in the concentration range from 5.76 × 10⁻⁶ M to 2.75 × 10⁻⁷ M, with a limit of detection (LOD) of 1.33 × 10⁻⁷ M. This method for the detection of procaine gave complementary results to the potentiometric one, which uses 5-COOH-3MPP as an electroactive material incorporated in a polyvinylchloride (PVC) membrane plasticized with o-NPOE. The detected concentration range by this ion-selective membrane electrode is wider (enlarged in the field of higher concentrations from 10⁻² to 10⁻⁶ M), linearly dependent with a 53.88 mV/decade slope, possesses a detection limit of 7 × 10⁻⁷ M, a response time of 60 s, and has a certified stability for a working period of six weeks.

A Ni/Cu-containing phosphinate material based on 2-carboxyethyl(phenyl)phosphinic acid was synthesized under hydrothermal conditions and characterized using FT-IR (Fourier Transform Infrared Spectroscopy), SEM (Scanning Electron Microscopy) and EDAX (Energy Dispersive X-ray Analysis) analysis. The FT-IR spectra suggest the coordination of the phosphinate group to the metal, while SEM revealed compact aggregated particles of the compound. EDAX analysis confirmed the simultaneous presence of both Ni(II) and Cu(II) metals in the synthesized material. DFT (Density Functional Theory) calculations performed on the corresponding mononuclear Ni-CEPPA and Cu-CEPPA models indicated that the Cu complex possesses a smaller HOMO–LUMO energy gap (2.72 eV) than the Ni analog (3.43 eV), suggesting higher electronic reactivity. The obtained material was preliminarily evaluated for Methylene Blue removal, exhibiting an adsorption capacity of 170.24 mg/g. These results suggest that mixed Ni/Cu phosphinate materials may represent potential candidates for adsorption-related applications.

A nickel(II) coordination material derived from 2-carboxyethyl(phenyl)phosphinic acid (CEPPA) was obtained under hydrothermal conditions and investigated by elemental analysis, Fourier-Transform Infrared spectroscopy (FT-IR), Scanning Electron Microscopy coupled with Energy-Dispersive X-ray analysis (SEM/EDX), Thermogravimetric Analysis (TGA), and Powder X-ray Diffraction (PXRD). Indexing and powder-profile refinement of the PXRD data support a monoclinic crystalline phase. FT-IR data are consistent with ligand deprotonation and changes in the phosphinate/carboxylate environments upon reaction with Ni(II), without assigning a unique coordination mode from vibrational data alone. The material was incorporated into a PVC/o-NPOE membrane containing NaTPB and evaluated for potentiometric naloxone detection. A linear response was obtained over 10⁻²–10⁻⁵ M with a slope of 52.67 mV decade⁻¹ and an experimental detection limit of 8.5 × 10⁻⁶ M. The results demonstrate the feasibility of integrating the Ni(II)–CEPPA material into a polymeric sensing membrane, while definitive atomic-level structural assignment and specific recognition interactions require additional structural and mechanistic evidence.