Zinc 2-((2-(benzoimidazol-2-yl)quinolin-8-ylimino)methyl)phenolates : synthesis, characterization and photoluminescence behavior

A series of 2-(2-(1H-benzoimidazol-2-yl)quinolin-8-yliminomethyl)phenol derivatives and their zinc complexes (C1 – C5) were synthesized and fully characterized. The molecular structure of the representative complex C2 was determined by single crystal X-ray diffraction, which revealed that the zinc was five-coordinated with the tetra-dentate ligand and a methanol bound to the metal afford a distorted square-pyramidal geometry. The UV-Vis absorption and fluorescence spectra of the organic compounds and their zinc complexes were measured and investigated in various solvents such as methanol, THF, dichloromethane, and toluene; significant influences by solvents were observed on their luminescent properties; red-shifts for the zinc complexes were clearly observed in comparisons to the free organic compounds

Towards Trigonal Prismatic Hexanuclear Copper Complexes For Catalytic Water Oxidation

Our planet is running out of energy resources and traditional renewables are not easily transported nor will be sufficient to cover the void left by fossil fuels. Therefore, a new energy storage system needs to be adopted. The medium with highest energy density that is readily available is hydrogen from water. However, to access hydrogen, water needs to be oxidized and water oxidation catalysts (WOCs) will be required for widespread adoption. In pursuit of WOCs, several hexauclear copper complexes were synthesized and characterized, including the isolation and characterization of a mixed-valent Cu6 (formally, CuII5CuIII) complex. Furthermore, early in the research, several novel coordination polymers (CPs) were serendipitously synthesized. This dissertation is divided into three major parts: (i) A series of trigonal prismatic Cu6-pyrazolato complexes (Cu6) form a unique arrangement of two O2- ions in a favorable position to form an O-O bond without much external influence. The Cu6 complexes undergo two reversible one-electron oxidations and a structurally characterized one-electron oxidized mixed-valent complex displays an O···O distance ~0.3 Å closer than the homovalent compound, which highlights the propensity of the system towards O-O bond formation. Spectroscopic findings and DFT calculations on the electronic structure of the mixed-valent Cu6-complex are reported. The results support the hypothesis that a variation of a Cu6 motif could function as a water oxidation catalyst. (ii) Three new coordination polymers containing trinuclear Cu(II)-4-formyl pyrazolato units connected by formyl group coordination were prepared and the crystal structures are reported: a 1D polymer formed by linking secondary building units (SBUs) and two 3D polymers with novel topologies consist of 14-nodal 3842,54-c and 3-nodal 3,3,4-c nets, respectively. (iii) Two new motifs of Cu6-pyrazolato complexes were prepared. One motif has two pyrazolato bridges between the trinuclear copper subunits with a µ4-Cl situated inside the open cage, and the other has the subunits bridged by a single pyrazolato ligand. Variable low-temperature NMR and magnetic studies were conducted. And for the first time, far-infrared spectroscopy studies were used to determine the characteristic absorptions of various coordination bonds in copper pyrazolate complexes

Tuning the Coordination Properties of Pyrazoles towards Specific Applications via Judicial Choice of Peripheral Substitution

The tunability of pyrazoles make them probably the most versatile ligands, and this is one of the right reasons to its use. Pyrazolyl ligands have intrinsic antibacterial property. Synthesis of pyrazolyl complexes with silver can be of great interest in biological applications. The urgent need to find alternative of currently used antibiotics has been recognized as a major challenge of the 21st century. Many ideas have been proposed, but re-emergence silver could be the most promising alternative to overcome the limitations of these antibiotics. In spite of the popularity of Sonogashira coupling reactions, there is still a room to improve the catalytic system to overcome the existing limitations. N-N donor ligands with palladium metal have shown better catalysis over the conventional ones. This work presents the synthesis of pyrazolyl ligands and their complexes with silver, palladium and mercury and exploring their applications accordingly. The work has been divided into four distinct regions of applications as follows. Eight new silver pyrazolyl complexes with triphenyl phosphine or 1,3,5-triaza-7-phosphaadamantane as a co-ligand have been synthesized, characterized with single crystal X-ray, spectroscopic techniques and elemental analyses and their antibacterial property against Pseudomonas aeruginosa was investigated with a soft tissue and skin infection model. Water soluble complex was found to be more efficient than silver nitrate. This compound releases Ag+ slower than AgNO3 and inhibits the physiological problems associated with the rapid release of Ag+. Five new tripodal (1R) pyrazolyl ligands were synthesized and their application in selective sensing of picric acid (PA) was successfully investigated. They are promising in sensing the picric acid in all physical states. Seven new mercury pyrazolyl complexes with broad versatility in geometry and nuclearity were synthesized. Two of them were used to extract mercury (Hg2+) from the mixture of Ln3+ in aqueous solution using chloroform as extractant and found promising. Nine palladium pyrazolyl complexes including three water soluble ones were synthesized. Two of them were used to catalyze the Sonogashira cross coupling reactions. The catalysts worked well in copper free, open air and mild reaction conditions. Reactivity of Pd-hexamer was also studied

Luminescent Cyclometalated Platinum and Palladium Complexes with Novel Photophysical Properties

abstract: Organic light emitting diodes (OLEDs) is a rapidly emerging technology based on organic thin film semiconductors. Recently, there has been substantial investment in their use in displays. In less than a decade, OLEDs have grown from a promising academic curiosity into a multi-billion dollar global industry. At the heart of an OLED are emissive molecules that generate light in response to electrical stimulation. Ideal emitters are efficient, compatible with existing materials, long lived, and produce light predominantly at useful wavelengths. Developing an understanding of the photophysical processes that dictate the luminescent properties of emissive materials is vital to their continued development. Chapter 1 and Chapter 2 provide an introduction to the topics presented and the laboratory methods used to explore them. Chapter 3 discusses a series of tridentate platinum complexes. A synthetic method utilizing microwave irradiation was explored, as well as a study of the effects ligand structure had on the excited state properties. Results and techniques developed in this endeavor were used as a foundation for the work undertaken in later chapters. Chapter 4 introduces a series of tetradentate platinum complexes that share a phenoxy-pyridyl (popy) motif. The new molecular design improved efficiency through increased rigidity and modification of the excited state properties. This class of platinum complexes were markedly more efficient than those presented in Chapter 3, and devices employing a green emitting complex of the series achieved nearly 100% electron-to-photon conversion efficiency in an OLED device. Chapter 5 adapts the ligand structure developed in Chapter 4 to palladium. The resulting complexes exceed reported efficiencies of palladium complexes by an order of magnitude. This chapter also provides the first report of a palladium complex as an emitter in an OLED device. Chapter 6 discusses the continuation of development efforts to include carbazolyl components in the ligand. These complexes possess interesting luminescent properties including ultra-narrow emission and metal assisted delayed fluorescence (MADF) emission.Dissertation/ThesisPh.D. Materials Science and Engineering 201

Mercury Clathration-Driven Phase Transition in a Luminescent Bipyrazolate Metal−Organic Framework: A Multitechnique Investigation

Mercury is one of the most toxic heavy metals. By virtue of its triple bond, the novel ligand 1,2-bis(1H-pyrazol-4- yl)ethyne (H2BPE) was expressly designed and synthesized to devise metal−organic frameworks (MOFs) exhibiting high chemical affinity for mercury. Two MOFs, Zn(BPE) and Zn(BPE)·nDMF [interpenetrated i-Zn and noninterpenetrated ni-Zn·S, respectively; DMF = dimethylformamide], were isolated as microcrystalline powders. While i-Zn is stable in water for at least 15 days, its suspension in HgCl2 aqueous solutions prompts its conversion into HgCl2@ni-Zn. A multitechnique approach allowed us to shed light onto the observed HgCl2-triggered i-Zn-to- HgCl2@ni-Zn transformation at the molecular level. Density functional theory calculations on model systems suggested that HgCl2 interacts via the mercury atom with the carbon−carbon triple bond exclusively in ni-Zn. Powder X-ray diffraction enabled us to quantify the extent of the i-Zn-to-HgCl2@ni-Zn transition in 100−5000 ppm HgCl2 (aq) solutions, while X-ray fluorescence and inductively coupled plasma-mass spectrometry allowed us to demonstrate that HgCl2 is quantitatively sequestered from the aqueous phase. Irradiating at 365 nm, an intense fluorescence is observed at 470 nm for ni-Zn·S, which is partially quenched for i-Zn. This spectral benchmark was exploited to monitor in real time the i-Zn-to-HgCl2@ni-Zn conversion kinetics at different HgCl2 (aq) concentrations. A sizeable fluorescence increase was observed, within a 1 h time lapse, even at a concentration of 5 ppb. Overall, this comprehensive investigation unraveled an intriguing molecular mechanism, featuring the disaggregation of a water-stable MOF in the presence of HgCl2 and the self-assembly of a different crystalline phase around the pollutant, which is sequestered and simultaneously quantified by means of a luminescence change. Such a case study might open the way to new-conception strategies to achieve real-time sensing of mercury-containing pollutants in wastewaters and, eventually, pursue their straightforward and costeffective purification.University of Insubria for partial fundingPrograma Juan de la Cierva Formación (FJC2020-045043-I)MCIN/AEI/10.13039/501100011033European Union NextGenerationEU/PRTR (Grants PID2020- 113608RB-I00 and TED2021-129886B-C41