Context <p>The structural, thermodynamic, and electronic properties of dodecahydrospiro[isothiochromene-3,2′-thiopyran] compounds with hydrogen and methyl substituents were systematically investigated using Density Functional Theory (DFT) to understand how substituent type and solvent polarity influence conformational stability and electronic structure in sulfur-containing heterocycles. Conformational preferences between axial and equatorial isomers were analyzed based on Gibbs free energy differences, anomeric effects, dipole moments, and key orbital interactions such as <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$L{P}_{ax}{X}_{7}\to {\sigma }_{{C}_{2}-{C}_{3}}^{*}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>L</mi> <msub> <mi>P</mi> <mrow> <mi mathvariant="italic">ax</mi> </mrow> </msub> <msub> <mi>X</mi> <mn>7</mn> </msub> <mo stretchy="false">→</mo> <mmultiscripts> <mi>σ</mi> <mrow> <msub> <mi>C</mi> <mn>2</mn> </msub> <mo>-</mo> <msub> <mi>C</mi> <mn>3</mn> </msub> </mrow> <mrow> <mrow /> <mo>∗</mo> </mrow> </mmultiscripts> </mrow> </math></EquationSource> </InlineEquation>, which influence bond lengths like <InlineEquation ID="IEq2"> <EquationSource Format="TEX">${r}_{{C}_{2}-{X}_{7}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>r</mi> <mrow> <msub> <mi>C</mi> <mn>2</mn> </msub> <mo>-</mo> <msub> <mi>X</mi> <mn>7</mn> </msub> </mrow> </msub> </math></EquationSource> </InlineEquation>. This comprehensive approach provides insight into how substituent type and environment influence the conformational stability and electronic characteristics of sulfur-containing heterocycles.</p> Methods <p>All quantum chemical calculations were carried out using the B3LYP functional within the DFT framework and the B3LYP/6-311+G** basis set. Natural Bond Orbital (NBO) analysis was employed to evaluate donor–acceptor interactions, stabilization energies, and orbital delocalizations. Solvent effects were incorporated using the Polarizable Continuum Model (PCM) for both polar (water) and non-polar (n-hexane) solvents, alongside gas-phase calculations. Computational analyses were performed with Gaussian 09W, and the conformational behavior of axial and equatorial isomers was assessed by determining Gibbs free energy differences (∆G), anomeric effects (AE), dipole moments (<InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\Delta \mu$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Δ</mi> <mi>μ</mi> </mrow> </math></EquationSource> </InlineEquation>), stabilization energies (<InlineEquation ID="IEq4"> <EquationSource Format="TEX">${E}_{2}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>E</mi> <mn>2</mn> </msub> </math></EquationSource> </InlineEquation>), donor–acceptor transitions, and structural parameters.</p>

Theoretical and computational studies on the conformation of dodecahydrospiro[isothiochromene-3,2′-thiopyran] compounds using Density Functional Theory (DFT) methods and Natural Bond Orbital (NBO) analysis

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发表日期：

2026年2月17日

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Pingfang Yuan,
Akram Banapour

摘要

Context

The structural, thermodynamic, and electronic properties of dodecahydrospiro[isothiochromene-3,2′-thiopyran] compounds with hydrogen and methyl substituents were systematically investigated using Density Functional Theory (DFT) to understand how substituent type and solvent polarity influence conformational stability and electronic structure in sulfur-containing heterocycles. Conformational preferences between axial and equatorial isomers were analyzed based on Gibbs free energy differences, anomeric effects, dipole moments, and key orbital interactions such as $L{P}_{ax}{X}_{7}\to {\sigma }_{{C}_{2}-{C}_{3}}^{*}$ $L P_{ax} X_{7} \to σ_{C_{2} - C_{3}}^{*}$ , which influence bond lengths like ${r}_{{C}_{2}-{X}_{7}}$ $r_{C_{2} - X_{7}}$ . This comprehensive approach provides insight into how substituent type and environment influence the conformational stability and electronic characteristics of sulfur-containing heterocycles.

Methods

All quantum chemical calculations were carried out using the B3LYP functional within the DFT framework and the B3LYP/6-311+G** basis set. Natural Bond Orbital (NBO) analysis was employed to evaluate donor–acceptor interactions, stabilization energies, and orbital delocalizations. Solvent effects were incorporated using the Polarizable Continuum Model (PCM) for both polar (water) and non-polar (n-hexane) solvents, alongside gas-phase calculations. Computational analyses were performed with Gaussian 09W, and the conformational behavior of axial and equatorial isomers was assessed by determining Gibbs free energy differences (∆G), anomeric effects (AE), dipole moments ( $\Delta \mu$ $Δ μ$ ), stabilization energies ( ${E}_{2}$ $E_{2}$ ), donor–acceptor transitions, and structural parameters.