Integrating a Smartphone and Molecular Modeling for Determining the Binding Constant and Stoichiometry Ratio of the Iron(II)–Phenanthroline Complex: An Activity for Analytical and Physical Chemistry Laboratories

Abstract

The binding constant and stoichiometry ratio for the formation of iron(II)−(1,10-phenanthroline) or iron(II)−o-phenanthroline complexes has been determined by a combination of a low-cost analytical method using a smartphone and a molecular modeling method as a laboratory experiment designed for analytical and physical chemistry courses. Intensity values were obtained from the digital images by measuring the RGB (red, green, blue) values (on a scale of 0−255 in intensity) of the samples between Fe(II) and ophenanthroline using a digital camera from a smartphone. The R channel showed the best linearity for predicting the binding constant. For computational studies, iron(II) complexes using water molecules and 1,10-phenanthroline were used to evaluate the stability of the complex by varying the number of ligands. Complexes have been optimized by reaching a minimum amount of energy. It was possible to observe how stable the complexes are from the optimization calculations, including aspects about the achieved geometries. The approach provides a simple method for performing stability constants over a wide range of complexes, from the undergraduate chemistry laboratories, in the field, and in the research laboratory.

Suppression of a BAHD acyltransferase decreases p‐coumaroyl on arabinoxylan and improves biomass digestibility in the model grass Setaria viridis

“…For the energy analysis, the PM7 semi‐empirical method was used to study the interaction energies of the 4‐Å cut‐off radius from p CA, FA, p CA‐Ara f or FA‐Ara f with BAHD proteins structures. The interaction energy (de Morais et al ., 2016), E bind, or binding energy, is defined as:where H f (complex) is the enthalpy of formation of complex, H f (ligand) is the enthalpy of formation of the isolated ligands ( p CA, FA, p CA‐Ara f or FA‐Ara f ) and H f (BAHD) is the enthalpy of formation of isolated BAHD structures.…”

Equilibrium Constant Determination Using Digital Images

“…2: − 10 ( 0 ) = − 10 ( ) = = O desenvolvimento de métodos quantitativos utilizando imagens digitais é cada vez mais utilizada para fins educativos e científicos. [10][11][12][13][14][15][16][17][18][19] Neste experimento, a concentração do complexo vermelho [Fe(H2O)5(SCN)] 2+ é determinada através da absorbância, mensurada em 447 nm, e dos valores de RGB extraídos de imagens digitais, obtidos com um scanner de mesa.…”

“…20 O modelo RGB é o modelo mais utilizado em imagens digitais, neste modelo as cores são compostas por combinações lineares das cores primárias, vermelho (Red), verde (Green) e azul (Blue), portanto, neste sistema toda cor pode ser definida como um vetor com três coordenadas (R, G, B) e os valores podem variar de 0 a 255, ou seja, são possíveis mais de 16,77 milhões (255 3 ) de combinações diferentes de cores. 20 Imagens digitais obtidas com scanners e smartphones são utilizadas em substituição a absorbância mensurada com um espectrofotômetro, 19 como, por exemplo, determinar a concentração de vitamina C em suplementos alimentares, 10 determinação da constante de equilíbrio, 13 determinação da concentração de proteínas, 15 atividade da amilase, 16 concentração de cobre na cachaça, 21 diagnostico de dengue, 22 classificação de águas minerais, 23 quantificação de manganês em pilhas, 24 quantificação de fosfato em refrigerante, 25 dureza e alcalinidade da água, 26 acidez de vinho tinto, 27 determinação da concentração de ferro em água e em alimentos, 28,29 quantificação de estreptomicina em medicamentos, 30 determinação da percentagem etanol em bebidas, 31 quantificação do corante (sunset yelloow) em alimentos, 32 quantificação de ácido salicílico 33 e adulteração do álcool combustível. 34…”

Finding the pKa Values of a Double-Range Indicator Thymol Blue in a Remote Learning Activity

“…Digital image capturing devices have successfully been employed in colorimetric measurements of various analytes from metal ions, − organic dyes, ,, and biochemical samples involving proteins and enzymes − (see ref for review). Because of its portability and ubiquity, students can perform colorimetric chemistry experiments at home using a smartphone to create a standard calibration curve and identify the concentration of an unknown .…”