SYNTHESIS, CHARACTERISTICS, OF MIXED LIGAND COMPLEX OF ZN(II) ION WITH 8-HYDROXYQUINOLINE AND BENZOIC ACID

SYNTHESIS, CHARACTERISTICS, OF MIXED LIGAND COMPLEX OF ZN(II) ION WITH 8-HYDROXYQUINOLINE AND BENZOIC ACID

CHAPTER ONE

INTRODUCTION

1.1       Background of Study

With the rate at which population is increasing and the usage of fossil fuels, the need for alternative and sustainable energy development has become a necessity. There is therefore need for energy saving materials that are affordable and that pose no threat to our environment. Areas of interests such as fuel cells, batteries, capacitors, solar cells, etc. afford much opportunity for improvement and research focus. (Lacey et al., 2014)

Detection of hazardous materials is a significant concern for homeland security, and portable sensors are potentially desirable to avoid the complexity of such materials, such as explosives. Luminescent metal organic frameworks (MOFs) are potentially useful as chemically-selective sensors.The study of luminescence behaviour in metal organic frameworks is an active area of research in inorganic chemistry. A large numberof 3d element have been employed to investigate the ligand luminescence. The most commonly reported metal organic framework structures are based on Zn²⁺ and Cd²⁺ ions, which have filled d orbitals and thus d–d transitions are not possible. In these compounds, intra-ligand and/or ligand metal charge transfer effects have been observed. The photoluminescence studies are important to understand the charge-transfer pathways. The studies on the luminescence behavior in MOFs clearly indicate that the energy transfer from the organic ligands to the metal center is easy. The life-time studies also suggest that the excited state possess considerable stability and allows for exploitation in many important applications. (Zhou, X et al., 2009; Konar et al., 2013)

Metal-organic frameworks (MOFs), also known as metal-organic networks, or coordination polymers, represent a new class of compounds containing metal ions linked by organic bridging ligands. A metal-organic framework (MOF) material can be thought of as the composition of two major components: a metal ion (or cluster of metal ions) and an organic molecule called a linker (or bridging ligands).

Metal ions       +         Organic linkers⎯⎯→    Coordination polymers/ MOFs

The organic ligands or linkers are groups that can donate multiple lone pairs of electrons (polydendate) to the metal ions, whereas the metal ions are made up of vacant orbital shells that can accept these lone pairs of electrons to form a metal-organic framework material.

Metal-organic framework materials are well-defined, adjustable and highly porous materials, with spatial confinement, often crystalline, sensitive to air and resistant to structural collapse upon heating. (Zang et al., 2006).

SYNTHESIS, CHARACTERISTICS, OF MIXED LIGAND COMPLEX OF ZN(II) ION WITH 8-HYDROXYQUINOLINE AND BENZOIC ACID