Energetic and structural properties of 4-nitro-2,1,3-benzothiadiazole

doi:10.1016/j.jct.2012.01.018

The Journal of Chemical Thermodynamics

Volume 49, June 2012, Pages 146-153

https://doi.org/10.1016/j.jct.2012.01.018 Get rights and content

Abstract

The energetic study of 4-nitro-2,1,3-benzothiadiazole has been developed using experimental techniques together with computational approaches. The standard (p^° = 0.1 MPa) molar enthalpy of formation of crystalline 4-nitro-2,1,3-benzothiadiazole (181.9 ± 2.3 kJ · mol⁻¹) was determined from the experimental standard molar energy of combustion −(3574.3 ± 1.3) kJ · mol⁻¹, in oxygen, measured by rotating-bomb combustion calorimetry at T = 298.15 K. The standard (p^° = 0.1 MPa) molar enthalpy of sublimation, at T = 298.15 K, (101.8 ± 4.3) kJ · mol⁻¹, was determined by a direct method, using the vacuum drop microcalorimetric technique. From the latter value and from the enthalpy of formation of the solid, it was calculated the standard (p^° = 0.1 MPa) enthalpy of formation of gaseous 4-nitro-2,1,3-benzothiadiazole as (283.7 ± 4.9) kJ · mol⁻¹. Standard ab initio molecular orbital calculations were performed using the G3(MP2)//B3LYP composite procedure and several working reactions in order to derive the standard molar enthalpy of formation 4-nitro-2,1,3-benzothiadiazole. The ab initio results are in good agreement with the experimental data.

Highlights

► Energetics of 4-nitro-2,1,3-benzothiadiazole: experimental computational study. ► $Δ_{f} H_{m}^{o}$ (cr) of 4-nitro-2,1,3-benzothiadiazole was measured by rotating combustion calorimetry. ► $Δ_{cr}^{g} H_{m}^{o}$ of 4-nitro-2,1,3-benzothiadiazole was derived from vacuum drop microcalorimetric measurements. ► Molecular orbital calculations for 4-nitro-2,1,3-benzothiadiazole were done by G3(MP2)//B3LYP.

Introduction

In the context of a systematic study on the thermochemical properties of diazole derivatives (figure 1), we have performed experimental and theoretical studies on the alkyl or phenyl substituent effects through the nitrogen atoms in pyrazole and imidazole rings [1], [2], which has been extended to include the effect of alkyl or aryl substituent in the carbon of the heterocycle of the bicyclic molecules derived from imidazole fused to an aromatic ring [3], [4], [5], [6], [7], in order to compare the effect of the substituent in the heterocycle of the bicyclic molecules with the corresponding monocyclic heteromolecules. On the other side, we have been also interested on the N–O dissociation bond in 2,1,3-benzoxadiazole-1-oxide (benzofuroxan) derivatives and this study requires the knowledge of data on the correspondent 2,1,3-benzoxadiazole (benzofurazan) derivatives, as it has been reported previously [8], [9], [10].

The purpose of this work is to study the 4-nitro-2,1,3-benzothiadiazole (figure 2), a molecule with two nitrogen atoms at 1 and 3 positions and one sulphur atom at 2 position in a di-unsaturated ring structure fused to a benzene ring that incorporates a nitro group on an adjacent position to the “junction” of the two cycles. The data reported for this compound affords the possibility to make comparisons with 4-nitro-benzofurazan [9] concerning the energetic effects on the presence of the sulphur instead an oxygen heteroatom on the benzodiazole ring. The nitro derivatives of benzazoles have found a wide range of applications, from medicine to agriculture to materials chemistry. Benzothiadiazole derivatives are well known for their biological activities such as inducers of systemic resistance to diseases rather than direct antifungal or antibacterial activities [11], [12]. More recently, 2,1,3-benzothiadiazole derivatives were prepared and copolymerized with thiophene derivatives using cross-coupling reactions, resulting materials exhibiting a reduced band gap that were explored in polymer photovoltaic devices [13], [14].

Section snippets

Purification and purity control of 4-nitro-2,1,3-benzothiadiazole

The 4-nitro-2,1,3-benzothiadiazole [CAS 6583-06-8] was purchased from Aldrich Chemical Company (99%) and re-crystallized three times from absolute ethanol. The melting point temperature of the re-crystallized sample, measured in a melting point apparatus, Stuart Scientific SMP2, was T = 383 K. Elemental analyses were in good agreement with expected values for C₆H₃N₃O₂S; found: C, 0.3971; H, 0.0173; N, 0.2315; calculated: C, 0.3979; H, 0.0167; and N, 0.2319 mass fractions. The compound has been

Computational details

The computational study of the 4-nitro-2,1,3-benzothidiazole consisted on the design of several gas-phase work reactions [34], [35], [36], [37] (to cancel errors in the calculations) and calculation of the energies of the species there included using the G3(MP2)//B3LYP method [38]. For each work reaction, the value of the enthalpy of formation in the gas-phase of the 4-nitro-2,1,3-benzothiadiazole was calculated from the variation of the enthalpy of the work reaction (equal to the sum of the

Enthalpy of formation in the crystalline phase

Rotating bomb combustion calorimetry was used to measure the energy of combustion of crystalline 4-nitro-2,1,3-benzothidiazole compound, from which the standard molar enthalpy of formation was derived. In the experiments with the title compound (C₆H₃O₂N₃S), the products of its combustion consist of a gaseous phase and an aqueous mixture of sulphuric acid for which the thermodynamics properties are known. Its combustion reaction is represented by the following equation: $C_{6} H_{3} O_{2} N_{3} S (cr) + 7.25 O_{2} (g) +$

Final remarks

Good agreement is found between experimental (283.7 ± 4.9) kJ · mol⁻¹ and computational (286.2 ± 6.6) kJ · mol⁻¹ standard molar enthalpies of formation, at T = 298.15 K, of 4-nitro-2,1,3-benzothiadiazole in the gas-phase, which supports previous evidences that the computational approach considered in this work is an excellent choice when dealing with sulphur-containing compounds [50].

The $Δ_{f} H_{m}^{\circ} (g)$ obtained in this work for 4-nitro-2,1,3-benzothiadiazole together with the values of 2,1,3-benzothiadiazole [51]

Acknowledgements

Thanks to Fundação para a Ciência e a Tecnologia, Lisbon, Portugal, for financial support to Centro de Investigação em Química of the University of Porto (CIQ – UP) and to FEDER for financial support to the research project POCTI/44471/QUI/2002.

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Energetic and structural properties of 4-nitro-2,1,3-benzothiadiazole

Abstract

Highlights

Introduction

Section snippets

Purification and purity control of 4-nitro-2,1,3-benzothiadiazole

Computational details

Enthalpy of formation in the crystalline phase

Final remarks

Acknowledgements

J. Chem. Thermodyn.

J. Chem. Thermodyn.

J. Chem. Thermodyn.

J. Chem. Thermodyn.

Thermochim. Acta

Thermochim. Acta

J. Chem. Thermodyn.

J. Chem. Thermodyn.

J. Organomet. Chem.

Tetrahedron

Chem. Phys. Lett.

J. Phys. Chem. A

Mol. Phys.

J. Chem. Thermodyn.

J. Phys. Chem. A

J. Chem. Thermodyn.

J. Phys. Chem. Ref. Data

The Plant Cell

Environmental Chemistry

Adv. Funct. Mater.

Chem. Mater.

Pure Appl. Chem.

Pure Appl. Chem.

Thermochim. Acta