Nawaz Rasool 1
Abstract
Charge transfer compounds of the donors (PHT), (BNZ) and (MBT) with the acceptors of (CHL) have been studied spectrophotomerically in ethanol as solvent. The stoichiometry of the reactions determined from photometric titration methods which was found at 1:1. The physical parameters of the CT complexes were evaluated by the Bensi-Hildebrand equation. The data of the new complexes are discussed in terms molar extinction coefficient (εCT), formation constant (KCT), Standard free energy (ΔG°), enthalpy (ΔH°), an entropy changes (ΔS°), oscillator strength (f), transition dipole moment (μEN), Ionization potential (IP) and resonance energy (RN). The formation of the complexes has been confirmed by UV-Vis, FT-IR, 1H-NMR and TGA/DTA the structural morphology was investigating by scanning electron microscope (SEM), transmission electron microscope (TEM) and x-Ray diffraction (XRD), and show these complexes in nanosize.
Keywords
Charge Transfer, phthalimide, Benzamide, 2-Mercaptobenzothiazole, Chloranil and Chloranilic acid.
Introduction
CT complexes represent the association of electron donor and the electron acceptor in order to observe the transition of electronic charge-transfer between the molecules. The CT complexes are identified in a spectral manner as they are formed between the two components. This can be truly maintained particularly when one of these components is a good electron donor and the other is a good electron acceptor. The transition of the electron is associated with the transfer of an electron from a good donor, which has a low potential of ionization, to a good acceptor, which has a high affinity of an electron (25).
The process in which the electron transfers from one atom to another, or from one molecule to another is called electron transfer which is considered the mechanism of redox thermodynamic concept description. To illustrate the reaction of redox, it is the chemical reaction that exists between the centers of metal ion that involve electron’s movement from the reductant to the oxidant that each of them has been reviewed and investigated, specifically in the past, by several worker’s groups. There are many acceptors like P-Benzoquinone, Chloranilic Acid, Picric Acid and Chloranil, which called complexing agents. The donor molecule should have small ionization energy (IP), while the acceptor molecule should have a large electron affinity (EA) to create CT in which the electron donor and electron acceptor interact and through the compound, the charge redistributes .The electron donor-acceptor (DA) attractions (or bonds) can be used to build multi- component networks in crystals, polymers, photoconductive polymers, and used as a dopant.In this regard, various studies focused the light on types of CT complexes that dominate a system of π and n-electron in which many applications occur, such as the inhibitor of electron transfer and the monomers in the polymer formation. In addition, they can be used in paper industry to produce colored paper as well as in photography. CT complexes are used for coloring materials, dendrimers and photo-catalyst. Moreover, CT complexes find some applications as in the storage of solar energy, studying redox process, molecular recognition, surface chemistry , and non-linear optical activity .
The electrical conductivity of charge transfer complexes of Thiozolers and Benzothiazoles with certain p-Chloranil (CHL) showed semiconducting behavior in the temperature range tested. The conductivity of both the complexes falls in the insulator range at 30°C. Based on the thermos gravimetric analysis in air, these complexes are thermally stable up to 90°C . The magnetic properties of charge transfer complexes
of the 2-amino-1,3,4-thiadiazole donor with p-Chloranil, o-Chloranil, and Chloranilic acid as acceptors show that these complexes have a paramagnetic character. The positive temperature coefficient of the electrical conductivity is evidence for the semiconducting character of these CT complexes.The X-ray structure of 2,9-dimethyl-1,10-phenanthroline (Me2Phen) with CHLA indicate the formation of diametric units [Me2phen]2[(CHLA)2] in which the two anions (CHLA)- are connected by two O—H….O hydrogen bonds whereas the cations and anions are joined together by strong three-center (bifurcated) N—H…..O hydrogen bonds. Furthermore, the cation is arranged in a π-π stacking.The X-ray structure of 2,9-dimric units ethyl-1,10-phennanthroline in (Me2Phen) with CHA indicate the formation of diametric unit [Me2Phen]2[(CHA)2] in which the two anions (CHA)- are connected by two O—H- – -O hydrogen bonds whereas the cations and anions are joined together by strong three-center (bifurcated) N—H- – -O hydrogen bonds. Furthermore, the cations is arranged in π-π stacking.Tetrathiafulvalene (TTF) with Halogen quinines such as: (TTF-QCl4) has been investigated by X-ray crystallographic, vibrational spectroscopy, and electrical measurements. In addition, when referring to this modular design as lock arm supramolecular ordering (LASO) this exhibiting ferroelectric Curie temperature of each structure, the dielectric constant along of the ferroelectric axis was measured. The networks order of an electron donor and acceptors are the nominee for organic ferroelectric due to the possible long-range orientation of their charge transfer dipoles. Besides, detect polarized optical spectroscopy, polarized ultraviolet-visible transmission
spectroscopy of these LASO, and employed to elucidate the various properties of the CT in these LASO networks.
Methodolgy:
Materials and Solutions:
Reagent grade phthalimide PHT from Aldrëch, Benzamide BNZ from Aldrëch, 2- mercaptobenzothiazole MBT from Aldrëc and chloranil (CHL) from Aldrëch were used without purification. Ethanol from Aldrëch as solvent .
Instrumentation and physical measurements:
Electronic Spectra:The electronic spectra of PHT, BNZ and MBT as donors with the resulted CT complexes prepared in ethanol. The Electronic spectra of PHT, BNZ and MBT as donors, resulted CT complexes in ethanol were recorded.
Photometric Titration: Photometric titration were performed at 25 ᴏC for the reactions of Phthalimide (PHT), Benzamide (BNZ) and 2-Mercaptobenzothiazole (MBT) with Chloranil (CHL) in Ethanol (EtOH) as solvent.
Synthesis of PHT-CHL BNZ-CHL and MBT-CHL Complexes:
The solid CT complex of Phthalimide with Chloranil PHT: CHL 1 mmol of the donor in 20ml of C2H5OH, a solutions of Chloranil was added (1 mmol) to the same amount if solvent in the same time drop by drop with continuously stirring for about 2 hours gradually heating. The EtOH was allowed to evaporate slowly with gradually heating. A yellow complex was formed, filtered, washed several times with little amount of methanol, and dried overnight with molecular mass 392.99 g/mol. The other CT complex with benzamide and 2-mercaptobenzothiazole, was prepared as the same of previous method but a yellow and gold colored complexes, was formed with molecular mass 267 and 413.11 g/mol .
