Cobalt(II) complex with new terpyridine ligand: An ab initio geometry optimization investigation

Synthesis and Structure of 2,5-Bis[N-(2,6-mesityl)iminomethyl]pyrrolylcobalt(II): Evidence for One-Electron-Oxidized, Redox Noninnocent Ligand Behavior

“…Finally, the presence of an intense and well-defined charge transfer band at 410 nm in the UV–vis spectrum is consistent with a metal-to-ligand charge transfer band where a d-based electron in the e orbital is excited into the vacancy in the low-lying π orbital (Figure ). Thus, the assignment as a high-spin d 7 Co­(II) complex of a noninnocent ligand is consistent with X-ray crystallographic metrics, measured values of magnetic susceptibility, EPR, IR, and UV–vis absorption spectra and corroborated by a wealth of existing literature on the geometric behavior of Co­(II) vs Co­(III) coordination complexes. − …”

“…Further, bulk magnetic susceptibility measurements using a Guoy balance and the Evans method on multiple samples reproducibly indicate (Mes 2 pyr)­CoCl 2 is an S = 2 system, as evidenced from the measured μ eff of 5.27 and 4.98 for the Guoy balance and Evans method, respectively (4.90 spin-only value of μ eff expected). These values are significantly higher than the expected spin-only value of ∼3.87 for a S = 3/2 Co­(II) system, and while spin–orbit coupling contributes additional angular momentum in S = 3/2 cobalt­(II) systems, giving values of μ eff in the range of 4.4–4.8 Bohr magnetons at room temperature, N-heterocyclic- and imine-based ligands tend to show much lower μ eff values − than we observe. Further, in the case where spin–orbit coupling contributes substantial angular momentum at room temperature, the temperature-dependent magnetic profiles of the systems are nonlinear, with μ eff dropping toward the spin-only value with decreasing temperature. − In contrast, solid-state magnetometry on (Mes 2 pyr)­CoCl 2 shows the value of μ eff is temperature independent (Figure S6), suggesting that our values of μ eff comprise predominantly the spin-only contribution and are therefore most consistent with an S = 2 spin quantum number.…”

Rational design of [Co(acacen)L2]+ inhibitors of protein function

“…24,25 This functional has been used for several studies of similar systems and shown to provide accurate results. [26][27][28][29][30] Optimization and frequency calculations of the lowest energy conformation of each structure were repeated using the same functional in conjunction with a correlation consistent, double zeta basis set (cc-pVDZ) to further validate results. Both basis sets produced structures that are in excellent agreement with X-ray crystal data, with Co-N and Co-O bond distances differing by less than 2 or 3% for calculations performed with 6-31G(d) and cc-pVDZ, respectively.…”