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High-pressure optical-absorption measurements performed on polycrystalline $\mathrm{Co}{(\mathrm{I}{\mathrm{O}}_{3})}_{2}$ samples were used to characterize the influence of pressure electronic $d--d$ transitions associated with ${\mathrm{Co}}^{2+}$ and fundamental band gap $\mathrm{Co}{(\mathrm{I}{\mathrm{O}}_{3})}_{2}$. The results shed light electron-lattice coupling show that exhibits an unusual behavior because compression Co--O bond distances is not coupled pressure-induced changes induced in unit-cell volume. Experimental internal have been explained based constituent $\mathrm{Co}{\mathrm{O}}_{6}$ octahedral units using semiempirical Tanabe-Sugano diagram. Our findings support high-spin ground state $(^{4}T_{1})$ very stable We also determined band-gap energy its dependence which highly nonlinear. According density-functional theory band-structure calculations, this nonlinearity occurs bottom conduction dominated by I-5p orbitals top valence Co-3d O-2p orbitals, I--O lengths exhibit different dependences.