Spectrochemical Properties and Solvatochromism of Tetradentate Schiff Base Complex with Nickel: Calculations and Experiments

JOYCE3.0: A General Protocol for the Specific Parametrization of Accurate Intramolecular Quantum Mechanically Derived Force Fields

While the intrinsically multiscale nature of most advanced materials necessitates the use of cost-effective computational models based on classical physics, a reliable description of the structure and dynamics of their components often requires a quantum-mechanical treatment. In this work, we present JOYCE3.0, a software package for the parametrization of accurate, quantum-mechanically derived force fields (QMD-FFs). Since its original release, the code has been extensively automated and expanded, with all novel implementations thoroughly discussed. To illustrate its general applicability, QMD-FFs are parametrized for seven benchmark cases, encompassing molecules with diverse structures and properties. These range from exotic stiff scaffolds, flexible polymeric chains, and polyenes of biological interest to transition-metal complexes. On the one hand, JOYCE3.0 FFs consistently outperform available general-purpose descriptions, achieving excellent agreement with higher-level theoretical methods or available experimental validation data. On the other hand, the remarkable accuracy found in the description of the molecular structures extends to electronic excited states, enabling the integration of the JOYCE3.0 QMD-FFs into multilevel protocols aimed at reliably predicting selected properties and spectral line shapes in advanced optoelectronic materials. The high quality of the results─spanning molecular structures, condensed-phase properties, and spectroscopic features─in combination with the enhanced interface with popular quantum-mechanical codes and molecular dynamics engines, as well as its applicability to chemically diverse species, strongly suggests that JOYCE3.0 could play a pivotal role in the rational design of functionalized materials and heterogeneous systems.

Fluorene-naphthalene Schiff base as a smart pigment in invisible ink with multiple security features for advanced anticounterfeiting and forensic applications

Smart functional materials with captivating optical properties are of immense importance due to their versatile applicability in anticounterfeiting and forensic science. A fluorene-naphthalene Schiff base (FNH) that displays aggregation induced emission, mechanofluorochromism and excitation wavelength dependent fluorescence inherent to the pristine and ground samples is synthesized. Water/solvent-based invisible security inks for flexo/screen printing were formulated using FNH as a smart pigment to check the originality of documents/branded products etc. The prints with good photostability, adherence to substrate and rub resistance are invisible in daylight showcasing multiple non-destructive and destructive techniques to authenticate the document. The inked area on UV dull paper substrate exhibits a weak emission, which is observed by the forger under UVA light. However, the user can validate the authenticity of the document by rubbing the print with hard objects, especially using a metal coin or glass rod to perceive a human eye detectable intensification in the orange fluorescence under the same illumination source. The intensity of the orange fluorescence reverts to the original, which enables the reuse of the security document after originality check. Yet another nondestructive authentication method is to observe a cyan fluorescence from the print and orangish yellow fluorescence from the rubbed printed region when shined with a 270-400 nm light source, whereas a cyanish green fluorescence both from the unrubbed and rubbed regions of the print when illuminated with a visible light source ranging from 420 to 480 nm. An additional verification through a destructive technique is to perceive red and yellow fluorescence of the ink film upon contact with THF and NaOH/KOH, respectively and a penetrating red fluorescence from the rear side of the THF-exposed printed area of the paper. The multi-level security features that cannot be easily replicated by the forger but allows a simple and easy validation process by the user are unique to FNH, used as a single pigment in the inks. Further, the applicability of the ground FNH in forensic science is established to distinctly observe Level I to II details of latent fingerprints.

Ni(II)-Salophen-Comprehensive Analysis on Electrochemical and Spectral Characterization and Biological Studies

New aspects of the Ni(II)-salophen complex and salophen ligand precursor were found during deep electrochemical and optical characterization, as well as biological studies for new pharmacological applications. Physicochemical and spectroscopic methods (¹H- and ¹³C-NMR, FT-IR and UV-Vis, electrospray ionization mass spectroscopy, thermogravimetric analysis, and molar conductance measurements) were also used to prove that the salophen ligand acts as a tetradentate and coordinates to the central metal through nitrogen and oxygen atoms. The electrochemical behavior of the free Schiff salophen ligand (H₂L) and its Ni(II) complex (Ni(II)L) was deeply studied in tetrabutylammonium perchlorate solutions in acetonitrile via CV, DPV, and RDE. Blue films on the surfaces of the electrodes as a result of the electropolymerization processes were put in evidence and characterized via CV and DPV. (H₂L) and Ni(II)L complexes were tested for their antimicrobial, antifungal, and antioxidant activity, showing good antimicrobial and antifungal activity against several bacteria and fungi.

Push–pull unsymmetrical substitution in nickel(ii) complexes with tetradentate N2O2 Schiff base ligands: synthesis, structures and linear–nonlinear optical studies

Push–pull unsymmetrical substitution efficiently modulates the electronic, linear and nonlinear optical properties of nickel(ii) complexes with salen-type ligands.