Through-bond (TB) and through-space (TS) substituent effects in substituted alkyl, alkenyl, and alkynyl arenes are quantified separately using molecular electrostatic potential (MESP) topographical analysis. The deepest MESP point over the aromatic ring (V(min)) is considered as a probe for monitoring these effects for a variety of substituents. In the case of substituted alkyl chains, the TS effect (79.6%) clearly dominates the TB effect, whereas in the unsaturated analogues the TB effect (∼55%) overrides the TS effect.

The quantification of inductive (I), resonance (R), and through-space (TS) effects of a variety of substituents (X) in cation-π interactions of the type C₆H₅X···Na⁺ is achieved by modeling C₆H₅-(Φ₁)(n)-X···Na⁺ (1), C₆H₅-(Φ₂)(n)-X···Na⁺ (2), C₆H₅-(Φ(2perpendicular))(n)-X···Na⁺ (2'), and C₆H₆ ···HX···Na⁺ (3), where Φ₁ = -CH₂CH₂-, Φ₂ = -CHCH-, Φ(2perpendicular) indicates that Φ₂ is perpendicular to the plane of C₆H₅, and n = 1-5. The cation-π interaction energies of 1, 2, 2', and 3, relative to X = H and fitted to polynomial equations in n have been used to extract the substituent effect E₀¹, E₀², E₀(2'), and E₀³ for n = 0, the C₆H₅X···Na⁺ systems. E₀¹ is made up of inductive (E(I)) and through-space (E(TS)) effects while the difference (E₀² - E₀(2')) is purely resonance (E(R)) and E₀³ is attributed to the TS contribution (E(TS)) of the X. The total interaction energy of C₆H₅X···Na⁺ is nearly equal to the sum of E(I), E(R), and E(TS), which brings out the unified view of cation-π interaction in terms of I, R, and TS effects. The electron-withdrawing substituents contribute largely by TS effect, whereas the electron-donating substituents contribute mainly by resonance effect to the total cation-π interaction energy.

In Ni(0)-catalyzed carboxylation reaction of aryl chloride with CO2, the formation of a Ni(I) species is crucial, because the CO2 insertion into the Ni(I)-Ph bond easily occurs but that into the Ni(II)-Ph bond cannot. This is a key point of this successful carboxylation reaction.