Design, Synthesis, and Characterization of Organometallic BODIPY-Ru(II) Dyads: Redox and Photophysical Properties with Singlet Oxygen Generation Capability†.

A series of Ru(II)-acetylide complexes (Ru1, Ru2, and Ru1m) with alkynyl-functionalized borondipyrromethene (BODIPY) conjugates were designed by varying the position of the linker that connects the BODIPY unit to the Ru(II) metal center through acetylide linkage at either the 2-(Ru1) and 2,6-(Ru2) or the meso-phenyl (Ru1m) position of the BODIPY scaffold. The Ru(II) organometallic complexes were characterized by various spectroscopic methods, including nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy, CHN, and high-resolution mass spectrometry (HRMS) analyses. The Ru(II)-BODIPY conjugates exhibit fascinating electrochemical and photophysical properties. All BODIPY-Ru(II) complexes exhibit strong absorption (εmax = 29,000-72,000 M-1 cm-1) in the visible region (λmax = 502-709 nm). Fluorescence is almost quenched for Ru1 and Ru2, whereas Ru1m shows the residual fluorescence of the corresponding BODIPY core at 517 nm. The application of the BODIPY-Ru(II) dyads as nonporphyrin-based triplet photosensitizers was explored by a method involving the singlet oxygen (1O2)-mediated photo-oxidation of diphenylisobenzofuran. Effective π-conjugation between the BODIPY chromophore and Ru(II) center in the case of Ru1 and Ru2 was found to be necessary to improve intersystem crossing (ISC) and hence the 1O2-sensitizing ability. In addition, electrochemical studies indicate electronic interplay between the metal center and the redox-active BODIPY in the BODIPY-Ru(II) dyads.

Functional Pyromellitic Diimide as a Corrosion Inhibitor for Galvanized Steel: An Atomic-Scale Engineering.

Corrosion of metal/steel is a major concern in terms of safety, durability, cost, and environment. We have studied a cost-effective, nontoxic, and environmentally friendly pyromellitic diimide (PMDI) compound as a corrosion inhibitor for galvanized steel through density functional theory. An atomic-scale engineering through the functionalization of PMDI is performed to showcase the enhancement in corrosion inhibition and strengthen the interaction between functionalized PMDI (F-PMDI) and zinc oxide (naturally existing on galvanized steel). PMDI is functionalized with methyl/diamine groups (inh1 (R = -CH3, R' = -CH3), inh2 (R = -CH3, R' = -CH2CH2NH2), and inh3 (R = -C6H3(NH2)2, R' = -CH2CH2NH2). The corrosion inhibition parameters (e.g., orbital energies, electronegativity, dipole moment, global hardness, and electron transfer) indicate the superior corrosion inhibition performance of inh3 (inh3 > inh2 > inh1). Inh3 (∼182.38 kJ/mol) strongly interacts with ZnO(101̅0) compared to inh2 (∼122.56 kJ/mol) and inh1 (∼119.66 kJ/mol). The superior performance of inh3 has been probed through charge density and density of states. Larger available states of N and H (of inh3) interact strongly with Zn and Osurf (of the surface), respectively, creating N-Zn and H-Osurf bonds. Interestingly, these bonds only appear in inh3. The charge accumulation on Osurf, and depletion on H(s), further strengthens the bonding between inh3 and ZnO(101̅0). The microscopic understanding obtained in this study will be useful to develop low-cost and efficient corrosion inhibitors for galvanized steel.

A water-soluble BODIPY based 'OFF/ON' fluorescent probe for the detection of Cd2+ ions with high selectivity and sensitivity.

A water-soluble dilithium salt BODIPY derivative (LiBDP) with appended dicarboxylate pseudo-crown ether [NO4] coordinating sites has been designed, synthesized and characterized successfully for the selective and sensitive recognition of Cd2+ in aqueous media. The chemosensor exhibits a remarkable increase in fluorescence intensity as well as a distinct color change upon the addition of Cd2+ over other environmentally and biologically relevant metal ions in H2O. The fluorometric response of LiBDP is attributed to the metal chelation-enhanced fluorescence (MCHEF) effect which has been confirmed by a strong association constant of 2.57 ± 1.06 × 105 M-1 and Job's plot, indicating 1 : 1 binding stoichiometry between LiBDP and Cd2+. Frontier molecular orbital analysis (obtained from DFT studies) also illustrates the turn-on fluorescence of the probe by blocking photoinduced electron transfer (PET) after coordination to Cd2+. The probe can detect Cd2+ in a competitive environment up to a submicromolar level in a biologically significant pH range. The sensor is proved to be reversible and reusable by the alternative addition of Cd2+ followed by S2-. The OFF/ON/OFF sensing behavior is utilized to construct an INHIBIT molecular logic gate based on the two inputs of Cd2+ and S2- and a fluorescence intensity at 512 nm as an output. The test paper experiment demonstrates the practical utility of LiBDP to monitor Cd2+ in an aqueous sample. Finally, the sensing probe was utilized to monitor Cd2+ in living cells.