Complexes of Furonewguinone B with a Cu 2+ Ion. A DFT Study
177
in the optimisation of one of these inputs. Some of the inputs undergoing this phenomenon were changed by removing O30 from the molecule, and they optimised
without any bond cleavage. Fig. S8 compares the outputs of some inputs differing
only by the presence or absence of O30. In the latter case, changes in the binding
sites may occasionally occur; an example is shown in the second row of fig. S8, with
the ion binds to the benzene ring and to π1 in the structure without O30. Although
many more cases should be considered to be able to make generalised inferences, it
may be suggested that the presence of O30 plays a relevant role for the cleavage of
the C26–C27 bond when the ion is close to π1.
3.4 Results in Solution
Calculations in solution were performed for all the uncomplexed conformers and for
the complexes with in-vacuo relative energy less than 26 kcal/mol, to ensure representativeness of binding sites and complexation effects. Table S18 reports the values
of relevant quantities (relative energies, energy lowering in solution, dipole moment,
free energy of solvation and its electrostatic component) in different media for the
uncomplexed conformers and the diagrams in fig. S9 highlight their trends. Table S19
reports the values of the same quantities in different media for the complexes, adding
the quantities specifically relevant to the complexes, such as the charge and the spin
density on the ion; the diagrams in fig. S10 highlight their trends and the diagrams
in fig. S11 highlight their ranges for complexes with the binding sites largely associated with lower relative energies (O25˛O30, O25˛O30˛O12, O8˛O18 and O30).
The quantities considered in these tables and figures are those that can be evaluated
realistically through PCM calculations, and provide information on the complexes’
stability and binding sites preferences in different media (through the relative energies) and on the molecule’s ability to reduce the ion (through the charge on the ion).
The MIA is not considered because its evaluation would involve the estimation of
the energy aspects of the partial desolvation of the molecule and the ion in the region
where they come into contact on complexation, and this evaluation is not easy using
a continuum solvent model [6].
Although acetonitrile has greater dipole moment than water, its effect on the properties of ACPLs is intermediate between that of chloroform and that of water (likely
because the greater dipole moment is related to greater distance between the charges,
not to the values of the charges). Therefore, on analysing results, the expression
«as the solvent polarity increases» is referred to the chloroform-acetonitrile-water
sequence and the expression «as the medium polarity increases» is referred to the
vacuum-chloroform-acetonitrile-water sequence.
The relative energies of the uncomplexed conformers in different media show
trends analogous to those of many ACPLs [26, 28], such as slight decrease of the
energy gaps in chloroform and acetonitrile with respect to in vacuo and greater
decrease in water, and some changes in the relative stabilities of the conformers
(more frequent and remarkable in water). The dipole moment increases as the medium
177
in the optimisation of one of these inputs. Some of the inputs undergoing this phenomenon were changed by removing O30 from the molecule, and they optimised
without any bond cleavage. Fig. S8 compares the outputs of some inputs differing
only by the presence or absence of O30. In the latter case, changes in the binding
sites may occasionally occur; an example is shown in the second row of fig. S8, with
the ion binds to the benzene ring and to π1 in the structure without O30. Although
many more cases should be considered to be able to make generalised inferences, it
may be suggested that the presence of O30 plays a relevant role for the cleavage of
the C26–C27 bond when the ion is close to π1.
3.4 Results in Solution
Calculations in solution were performed for all the uncomplexed conformers and for
the complexes with in-vacuo relative energy less than 26 kcal/mol, to ensure representativeness of binding sites and complexation effects. Table S18 reports the values
of relevant quantities (relative energies, energy lowering in solution, dipole moment,
free energy of solvation and its electrostatic component) in different media for the
uncomplexed conformers and the diagrams in fig. S9 highlight their trends. Table S19
reports the values of the same quantities in different media for the complexes, adding
the quantities specifically relevant to the complexes, such as the charge and the spin
density on the ion; the diagrams in fig. S10 highlight their trends and the diagrams
in fig. S11 highlight their ranges for complexes with the binding sites largely associated with lower relative energies (O25˛O30, O25˛O30˛O12, O8˛O18 and O30).
The quantities considered in these tables and figures are those that can be evaluated
realistically through PCM calculations, and provide information on the complexes’
stability and binding sites preferences in different media (through the relative energies) and on the molecule’s ability to reduce the ion (through the charge on the ion).
The MIA is not considered because its evaluation would involve the estimation of
the energy aspects of the partial desolvation of the molecule and the ion in the region
where they come into contact on complexation, and this evaluation is not easy using
a continuum solvent model [6].
Although acetonitrile has greater dipole moment than water, its effect on the properties of ACPLs is intermediate between that of chloroform and that of water (likely
because the greater dipole moment is related to greater distance between the charges,
not to the values of the charges). Therefore, on analysing results, the expression
«as the solvent polarity increases» is referred to the chloroform-acetonitrile-water
sequence and the expression «as the medium polarity increases» is referred to the
vacuum-chloroform-acetonitrile-water sequence.
The relative energies of the uncomplexed conformers in different media show
trends analogous to those of many ACPLs [26, 28], such as slight decrease of the
energy gaps in chloroform and acetonitrile with respect to in vacuo and greater
decrease in water, and some changes in the relative stabilities of the conformers
(more frequent and remarkable in water). The dipole moment increases as the medium