Biomimetic complexes of Co(II), Cu(II) and Ni(II) with 2-aminomethylbenzimidazole. EGA-MS characterization of the thermally induced decomposition

doi:10.1016/j.microc.2014.02.006

Microchemical Journal

Volume 115, July 2014, Pages 27-31

https://doi.org/10.1016/j.microc.2014.02.006 Get rights and content

Highlights

•
Six biomimetic complexes were precipitated and the thermal behavior was studied.
•
Evolved gas analysis by MS allowed one to prove the supposed decomposition mechanism.
•
The different influence of the reaction atmosphere was proved by the fragmentation pattern.

Abstract

Substituted benzimidazoles are a useful model ligand to simulate specific interactions in biomimetic complexes, since compounds that contain the imidazole ring of the histidine residue are good models of bioinorganic interest. In this study, Co(II), Cu(II) and Ni(II) complexes with 2-aminomethylbenzimidazole ligand, synthesized following the literature, were characterized by mass spectrometry evolved gas analysis (EGA-MS) that allowed one to describe their thermally induced decomposition.

Graphical abstract

Introduction

Complexes that contain the imidazole ring of the histidine residue are useful model compounds of bioinorganic interest [1], [2], [3], [4], [5], [6], [7], [8]. The imidazole ring is an essential metal binding site in metalloproteins (one or more imidazole units are bound to metal ions in almost all copper- and zinc-metalloproteins or e.g., in nickel-containing urease) and thus has profound effects on their biological actions [9], [10]. It is also well known that the amino group acts as the primary anchor site for metal ions and, as such, is able to promote the stepwise deprotonation and subsequent coordination of other successive binding sites, leading to the formation of the hydrolytically stable, fused, five-membered chelate rings with M–N bonds. Thus, complexes formed between metal ions and different types of bioligands, namely heteroaromatic nitrogen bases, may be considered as models for substrate–metal ion–enzyme interactions and other metal ion mediated biochemical interactions [11]. Recently, benzimidazole derived drugs have received much attention owing to the fact that benzimidazole residue is a constituent of vitamin B₁₂ which supports their potential use as therapeutics [12], [13]. The interest in 2-aminomethylbenzimidazole (2-AMBI) is also due to the fact that compounds containing this heterocycle have been shown to exhibit a broad spectrum of pharmacological activities [14], including a variety of antifungal [15], antibacterial [16], [17], antimicrobial [18], [19], antiamoebic [20], antiparasitic [21] and antitumor applications [22], [23]. Clinical examples include mebendazole and albendazole (antihelmintics) [24]. The antiviral activity of some 2-substituted benzimidazole derivatives is considered to be related to their ability to chelate trace metal ions in biological systems [25]. Additionally, 2-AMBI possesses two aromatic rings and one of them contains basic nitrogen (imidazole) and possesses π-accepting properties, which are expected to display a stability-enhancement due to the hydrophobic interaction with the substituted group of the amino acids or involved in the aromatic ring π–π stacking effects with purine and pyrimidine bases.

The scientific experience of the authors showed systematic behaviors of coordination compounds [26], [27], [28], [29], [30], enhanced by mass spectrometry [31], [32], [33], [34] and thermoanalytical techniques [35], [36], [37], [38], [39], [40], [41], [42].

To confirm the supposed general characteristic decomposition mechanism, the aim of this work was to study the thermally induced processes on six coordination compounds of general formula ML₂X₂ (where M = Co(II), Cu(II) or Ni(II), and X = Cl or Br). Complexes were precipitated following literature references [43], [44], [45] and characterized by elemental analysis and atomic spectroscopy. Evolved Gas Analysis performed by mass spectrometry (EGA-MS) was applied since this hyphenated technique is a very useful tool to solve analytical problems in several different fields [46], [47], [48], [49], [50], [51]. Experimental evidences proved the thermally induced decomposition mechanism.

Section snippets

Materials

2-Aminomethylbenzimidazole and the cobalt, copper and nickel chlorides and bromides were purchased from Aldrich and Merck. All the reagents were of A.R. grade and used without further purification. Several different procedures can be found in the literature to precipitate the complexes of general formula ML₂X₂, where M = Co(II), Cu(II) or Ni(II), and X = Cl or Br [43], [44], [45].

The generic reaction is shown in Scheme 1.

Several different attempts, following those reported in the literature, gave

Results and discussion

The results from the elemental analysis of the six precipitated complexes are reported in Table 1. Calculated and found element percent are in good agreement.

The thermally induced decomposition steps of the precipitated complexes were comparatively studied by mass spectrometry evolved gas analysis (EGA-MS). In Fig. 1, the thermoanalytical profiles of the chloride complexes are overlapped to compare the releasing steps when the purging flow is air.

The thermal decomposition is based on three main

Conclusions

Cobalt, Copper and Nickel chloride or bromide complexes with the 2-aminomethylbenzimidazole ligand were synthesized and characterized by elemental analysis and emission atomic spectroscopy.

Their thermally induced decomposition mechanism was studied by on-line coupling a mass spectrometer to a thermal analyzer. The resulting m/z traces from the Evolved Gas Analysis (EGA-MS) confirmed the decomposition mechanism.

Results showed that neither the different metal nor the different anion significantly

Acknowledgment

Authors acknowledge the help of Dr. L.W. Wo in the synthesis of the complexes.

References (51)

S. Materazzi et al.
Thermochim. Acta
(2013)
S. Materazzi et al.
Thermochim. Acta
(2007)
S. De Angelis Curtis et al.
Thermochim. Acta
(2010)
A. García-Raso et al.
Polyhedron
(2003)
W. Nawrocka et al.
Il Farmaco
(2004)
H. Küçükbay et al.
Il Farmaco
(2003)
A.A. El-Sherif et al.
Spectrochim. Acta A
(2007)
N.S. Pawar et al.
Eur. J. Pharm. Sci.
(2004)
S. Özden et al.
Bioorg. Med. Chem.
(2005)
G. Navarrete-Vázquez et al.
Bioorg. Med. Chem. Lett.
(2001)

C. Bretti et al.

Fluid Phase Equilib.

(2008)

F. Crea et al.

Talanta

(2008)

P. Cardiano et al.

J. Inorg. Biochem.

(2013)

M.L. Di Gioia et al.

J. Chromatogr. A

(2005)

S. Vecchio et al.

Thermochim. Acta

(2013)

S. De Angelis Curtis et al.

J. Anal. Appl. Pyrol.

(2010)

C. Perrino et al.

Atmos. Environ.

(2012)

S. Materazzi et al.

Thermochim. Acta

(2012)

Horacio Lopez-Sandoval et al.

J. Inorg. Biochem.

(2008)

S. Yurdakul et al.

J. Mol. Struct.

(2003)

E. Sahin et al.

J. Mol. Struct.

(2002)

S. Materazzi et al.

Talanta

(2006)

S. Materazzi et al.

Talanta

(2006)

K.D. Karlin et al.

Bioinorganic Chemistry of Copper

(1993)

T.J. Spiro

(1981)

Cited by (33)

TGA/Chemometrics addressing innovative preparation strategies for functionalized carbon nanotubes
2020, Journal of Pharmaceutical Analysis
In this work, functionalized carbon nanotubes (CNTs) using two polyamine polymers, polyethyleneimine (PEI) and polyamidoamine dendrimer (PAMAM), were investigated by thermal analysis in order to address preparation strategies to obtain low cytotoxic compounds with the ability to conjugate microRNAs and, at the same time, to transfect efficiently endothelial cells. Thermogravimetric analysis (TGA) was coupled to chemometrics as a novel analytical strategy to characterize functionalized CNTs from different preparation conditions. In particular, two starting materials were considered: very small CNTs and carboxylated CNTs (CNT-COOH) in order to examine the affinity with polymers. Chemometrics permitted to compare results from TGA and to investigate the effect of a number of factors affecting the synthesis of coated nanotubes including a different amount of involved polymer and the time required for the suspension for a satisfactory and reproducible preparation procedure. The results demonstrated the effectiveness of TGA as a tool able to address synthesis of coated CNTs to be employed as efficient drug delivery vectors in biomedical applications.
Monitoring of cannabinoids in hemp flours by MicroNIR/Chemometrics
2020, Talanta
Cannabinoids in hemp plant are strictly located in the inflorescence, in particular in top side of the plant while a lower amount may be found in the leaves. As a consequence, the lower amount of cannabinoids which can be recovered in the hemp flours is obtained from seeds, thus from contamination during harvesting procedures. To this aim, a screening test for the real time detection of cannabinoids in hemp flour was developed by a miniaturized analytical platform based on the MicroNIR spectrometer. Chemometrics was used to develop models of prediction to identify the cannabinoids and simultaneously to quantify the residual amounts in order to accomplish specific regulatory legislation according to the country. In particular, Partial Least Square-Discriminant Analysis (PLS-DA) and Partial Least Square regression (PLSr) were applied and results demonstrated that MicroNIR/Chemometric platform permit to differentiate hemp flours according to the presence of CBD, THC and CBG. In addition, for each cannabinoid, a quantification method was developed in the range 0.001–0.1 %ww, and their performances were evaluated by comparing results to those obtained by the reference procedures. Processing of the real samples provided a suitable correlation and confirmed the capabilities of this innovative platform to be used for the monitoring of the residual content of cannabinoids in hemp flours.
Real time detection of amphetamine in oral fluids by MicroNIR/Chemometrics
2020, Talanta
Citation Excerpt :
In this work, a novel analytical platform based on MicroNIR spectroscopy associated to chemometric analysis is proposed for a fast and accurate detection of AMP in non-pretreated oral fluids. The main advantage of this compact system is related to the miniaturized portable spectrometer operating in the Near Infrared region that permits to obtain comparable outcomes as the laboratory one because of its geometry and optical resolution [30–35]. In addition, the association with chemometrics provided an automated and non destructive tool able to simultaneously detect and quantify traces of AMP in oral fluids and permitted to further investigate the same oral fluid sample from consumer with the reference official procedure (GC-MS) for confirmatory analysis.
In this work, a novel coupled approach MicroNIR/Chemometrics based on a miniaturized and portable spectrometer is proposed for the on site detection of amphetamines (AMP) in non pretreated oral fluids. In particular, the coupling of MicroNIR with chemometrics was investigated with the aim of developing a fast and accurate approach able to perform the on-site prediction of AMP abuse. A predictive model to be used in real cases was developed by collecting specimens from volunteers and spiked samples with increasing amounts of AMP were prepared to optimize calibration. Partial Least Square-Discriminant Analysis (PLS-DA) and Partial Least Square regression (PLS) were involved to detect and quantify AMP. Results demonstrated that MicroNIR/Chemometric platform is statistically able to identify AMP abuse in simulated oral fluid samples containing, with the accuracy and sensitivity of the actual proposed official reference methods. The method was checked against false positive and true positive response and results proved to be those required for confirmatory analyses. This method would permit to simplify AMP abuse monitoring for roadside drug testing or workplace surveillance and may be of help at first aid points.
MicroNIR/Chemometrics: A new analytical platform for fast and accurate detection of Δ9-Tetrahydrocannabinol (THC) in oral fluids
2019, Drug and Alcohol Dependence
Citation Excerpt :
Nevertheless, Near Infrared spectroscopy has the advantage over Raman in detecting analytes in oral fluid composition such as amino acids. In addition, the coupling with chemometric tools provides models of prediction for qualitative as well as quantitative response with the required accuracy since the interference of the matrix in the spectral signal may be evaluated (Meesa et al., 2018; Risoluti et al., 2016; Materazzi et al., 2014a, b; Materazzi et al., 2014c, 2015; Kordi et al., 2017). The latest miniaturized NIR instrument is the MicroNIR, an ultra compact (45 mm in diameter and 42 mm in height) and portable device developed and distributed by Viavi Solutions (JDSU Corporation, Milpitas, CA), that weighs about 60 g and it is entirely powered (5 V) and controlled by a USB port of a portable computer (Risoluti et al., 2018; Risoluti and Materazzi, 2018).
Δ⁹-Tetrahydrocannabinol (THC) is already considered one of the most addictive substances since an increasing number of consumers/abusers of THC and THC based products are observed worldwide. In this work, the capabilities of a novel miniaturized and portable MicroNIR spectrometer were investigated in order to propose a practical and intelligible test allowing the rapid and easy screening of Δ⁹-Tetrahydrocannabinol (THC) oral fluids without any pretreatment.
Specimens from volunteers were collected in order to consider any sources of variability in the spectral response and spiked with increasing amount of THC in order to realize predictive models to be used in real cases. Partial Least Square-Discriminant Analysis (PLS-DA) and Partial Least Square regression (PLSr) for the simultaneously detection and quantification of THC, were applied to baseline corrected spectra pre-treated by first derivative transform.
Results demonstrated that MicroNIR/Chemometric platform is statistically able to identify THC abuse in simulated oral fluid samples containing THC from 10 to 100 ng/ml, with a precision and a sensitivity of about 1.51% and 0.1% respectively.
The coupling MicroNIR/Chemometrics permits to simplify THC abuse monitoring for roadside drug testing or workplace surveillance and provides the rapid interpretation of results, as once the model is assessed, it can be used to process real samples in a “click-on” device.
Updating procedures in forensic chemistry: One step cyanoacrylate method to develop latent fingermarks and subsequent DNA profiling
2019, Microchemical Journal
Citation Excerpt :
In fact, based on the Locard's principle of mutual exchange, reliable and performing approaches that may improve the fingermarks detection, are more and more required. A number of techniques have been proposed for fingermarks enhancement on various surfaces, including optical methods [1–3], physical methods such as powdering small particle reagents, vacuum metal deposition [4–7] and chemical treatment using ninhydrin, 1,8-diazafluoren-9-one (DFO), 1,2-indanedione (1,2-IND) [8] and genipin [9–12]. Nevertheless, more efficient reagents and methodologies are needed to detect fingermarks, especially when latent traces are involved [13].
Fingerprints play a key role in crime scene investigations because their friction ridges pattern can be used for identification purposes. In most cases, fingermarks are invisible and influenced by substrates or environmental factors. Latent fingermarks, on non-porous substrates, developed by traditional cyanoacrylate fuming process, often lack contrast with the substrates; therefore further enhancements are required, such as dye staining or powder dusting. This second step, that is part of the conventional detection, aims at improving contrast and at increasing the legibility of details. To avoid the second step, several commercially available formulations of cyanoacrylate have been recently manufactured and marketed as “one-step” fuming reagents for latent fingerprints visualization. In particular, Lumicyano is found to be very promising, combining the cyanoacrylate fuming and the dyeing procedures into a one-step process offering the potential to save time and effort in the detection of latent fingermarks.
In this work, a detailed comparative examination between conventional, two steps process (cyanoacrylate fuming followed by staining with Basic Yellow 40) and Lumicyano is proposed for fingerprints detection, in cooperation with the Scientific Investigation Department (Carabinieri-RIS) of Rome. The study has been conducted on fresh and aged fingermarks (up to 100 days) and applied to non-porous surfaces without changing the fuming chamber settings of forensic laboratories. Fingermarks has been detected with UV Reflection (λ₂₅₄) using SceneScope RUVIS instrumentation; furthermore, marks have been observed under white light and in fluorescence (λ₄₁₅ e λ₅₁₅) with crimescope system in order to ensure a good compatibility with the forensic light sources available within most police forces. The Lumicyano fluorescence decay was also evaluated up to 20 days. The possibility of further DNA detection after marks visualization, has also been investigated to propose a novel approach able to detect fingermarks and DNA from the same forensic trace. Furthermore, NMR analysis was performed to get some information about the interaction between the ethyl-2-polycyanoacrylate and 3-chloro-6-ethoxy-1,2,4,5-tetrazine (Lumicyano post fumigation) as well as to understand whether the fluorophore binds covalently the polymer formed on the ridges.
The results indicate that good ridges clarity and excellent contrast are observed with one-step process, concluding that Lumicyano detects fingermarks with equal or better sensitivity and ridge details than currently used cyanoacrylate, allowing marks' acquisition ever after 100 days. This study has shown that further enhancement with Basic Yellow 40 (BY40) after Lumicyano can still be carried out if required, allowing the visualization of marks using a different combination of incident/emission longwave, for best performing results. Moreover, Lumicyano was found to be compatible with a subsequent DNA. The results of NMR analysis show that there is no chemical covalent bond between fluorophore and polymer.
New methods for thalassemia screening: TGA/Chemometrics test is not influenced by the aging of blood samples
2019, Microchemical Journal
Citation Excerpt :
In particular, thermogravimetry was successfully applied to very different matrices [11–17] since no sample pretreatment is needed. The advances in multiparametric analyses in conjuction with the experience of our research group in developing coupled approaches [18–22], led to the optimization of a novel coupling based on thermogravimetry associated with chemometrics that demonstrated to be promising in different field [22,23]. Recently, the possibility of using Thermogravimetric analysis (TGA) in conjunction with Chemometrics as a new method for β-thalassemia detection has been proposed [23].
The coupling of Thermogravimetry (TG) in conjuction with chemometrics was investigated for the first time to evaluate the capabilities of this novel test to provide the screening of thalassemia in blood samples stored at 4 °C until 15 days. Healthy donors were considered as reference subjects and a typical thermal behaviour as a function of aging was estimated and compared to thermal behaviour of thalassemia subjects. Diagnosis of thalassemia was made at the Day-Hospital Thalassemia of S. Eugenio Hospital through a comprehensive assessment of clinical presentation and hematological and molecular analysis. Despite blood changes with aging, the application of the TGA/Chemometrics test reveal that healthy and thalassemic population may be significantly differentiated after 15 days from blood collection with a 100% of correct classification rate. This new method applied to aged samples was able to discriminate thalassemia in transfused patients that is generally not possible by the common first level protocol used for thalassemia screening, and in δβ-thalassemias, and β-thalassemia combined with Hb Lepore, usually requiring the molecular analysis for diagnosis. This study, for the first time, describes a screening method for thalassemia able to detect thalassemia on whole blood samples stored for 15 days.
In conclusion TGA/Chemometrics screening test for thalassemia is not influenced by the aging of blood samples and this approach could open the way to prevention programs for thalassemia also in the developing countries where expertise and facilities for their control are extremely limited or in situation involving delayed analyses.

View all citing articles on Scopus

View full text

Biomimetic complexes of Co(II), Cu(II) and Ni(II) with 2-aminomethylbenzimidazole. EGA-MS characterization of the thermally induced decomposition

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Materials

Results and discussion

Conclusions

Acknowledgment

Thermochim. Acta

Thermochim. Acta

Thermochim. Acta

Polyhedron

Il Farmaco

Il Farmaco

Spectrochim. Acta A

Eur. J. Pharm. Sci.

Bioorg. Med. Chem.

Bioorg. Med. Chem. Lett.

Fluid Phase Equilib.

Talanta

J. Inorg. Biochem.

J. Chromatogr. A

Thermochim. Acta

J. Anal. Appl. Pyrol.

Atmos. Environ.

Thermochim. Acta

J. Inorg. Biochem.

J. Mol. Struct.

J. Mol. Struct.

Talanta

Talanta

Bioinorganic Chemistry of Copper