Pi-Conjugated Phosphole Derivatives: Promising Building Blocks for ?-Conjugated Organic Materials

Pi-Conjugated organophosphorus derivatives have recently emerged as valuable building blocks for the tailoring of functional molecular materials. In order to guide the synthesis of novels materials with low band gaps, theoretical study on the geometries and electronic properties of new conjugated compounds based on low coordinate heterophosphole compounds were carried out. The theoretical ground-state geometries and the electronic structures of the studied molecules were obtained using the density functional theory (DFT) method at B3LYP level with 6-31G(d) basis set. The effects of the phosphorus and different heteroatom elements on the geometries and electronic properties of these materials were discussed. The results from this study show that conjugated molecules containing phosphorus atom gives better electronic properties compared to their organic counterparts that had been used in optoelectronic devices. Hence these compounds could be a good promising building blocks candidate for opto-electronic applications. Keywords: Conjugated Compounds, Electronic Properties, Density Functional Theory, Opto-Electronic Devic

Theoretical Study on Substituent's Effect on the Properties of Benzofused thieno [3, 2-b] Furan and its Isomeric Form

ABSTRACT: The theoretical study on the ground state properties of isomeric benzofused thieno [3,2-b]furans was carried out using semi-emperical AM1 and Density functional theory/B3LYP 6-31G* /6-31G* basis set. This was used in order to determine the effect of substituent; Br 2 , I 2 , OH -, on the stability, reactivity and other properties of the isomers. From the calculated values of E, μ, η, ω, ΔH-L obtained, it can be inferred that thieno [3,2-b]benzofuran is more aromatic, more stable and less reactive than isomeric benzothieno[3,2-b]furan. These results agree with the experimental result concerning the different reactivity and stability of both heterocyclic systems. The study of bond order uniformity, local ionization energy and electrostatic potential energy surfaces analysis revealed structural differences of isomeric thieno [3,2-b]furans that explains their reactivity features. Benzothieno[3,2-b]furan could be an analogue of aromatic benzothiophene substituted with C(2)=C(3) vinylic moiety. This evidently points out therefore that the electrophilic substitution reaction for benzothieno [3,2-b]furan goes via addition-elimination mechanism at the C(2)

Assessment of naturally occurring 40K, 232Th and 238U and their associated radiological hazard indices in soils used for building in Ondo West Local Government Area, Southwestern, Nigeria

The naturally occurring 40K, 232Th and 238U radionuclide contents in the soil used as building materials in Ondo West Local Government, Southwest Nigeria were determined using gamma spectrometric technique. The radiological hazards were estimated by employing several indices consisting of radium equivalent (Raeq), representative level index (RLI), activity utilization index (AUI), absorbed dose (D), annual effective dose, external hazard index (Hex), internal hazard index (Hin) and gamma index (Iᵧ). The average activity concentrations of 238U, 40K, 232Th and Raeq were 171.8, 146.2, 19.8 and 211. 3 Bqkg-1 while the average values of Hin, Hex, RLI, D, AED, ELCR, AUI and Iᵧ were, 1.0, 0.6, 0.2, 97.4, 0.5, 3.9 x 10-3, 1.8 and 0.7, respectively. The multivariate statistical analysis was employed to identify the relationships between the radionuclides and the estimated radiological hazard parameters. The estimated radiological indices were within the internationally acceptable limits confirming the safe use of these soil for building construction for human dwelling without any radiological implications