Rhenium(I) Tricarbonyl Complexes with Peripheral N-Coordination Sites: A Foundation for Heterotrimetallic Nonlinear Optical Chromophores

Abstract

The compounds 4,4′-dicyano-2,2′-bipyridyl (dcbpy), 4,4′-bis­(4-cyanophenyl)-2,2′-bipyridyl (bcpbpy), 4,4′-bis­[(E)-2-(4-cyanophenyl)­vinyl]-2,2′-bipyridyl (bcpvbpy), and 4,4′-bis­[(E)-2-(4-pyridyl)­vinyl]-2,2′-bipyridyl (bpvbpy) are used to prepare nine new complexes with fac-{ReI(CO)3(L)} n+ (L = Cl–, MeCN, pyridine (py), or 4-cyanopyridine (cpy)) centers. The cationic complexes are isolated as their OTf– salts. These new monometallic species are studied together with the known fac-ReICl­(CO)3(qpy) (qpy = 4,4′:2′,2″:4″,4‴-quaterpyridyl) (de Wolf, P.; et al. Inorg. Chim. Acta 2003, 355, 280–285). Coordination of {RuII(NH3)5}2+ centers to the peripheral N atoms of fac-ReICl­(CO)3(qpy) and fac-[ReI(CO)3(bcpbpy)­(py)]+ affords heterotrimetallic complexes that are isolated as their PF6 – salts. Single-crystal X-ray structures are reported for the solvates fac-ReICl­(CO)3(dcbpy)·Me2CO, fac-[ReI(CO)3(dcbpy)­(MeCN)]­OTf·PhMe, fac-[ReI(CO)3(dcbpy)­(py)]­OTf·0.5PhMe, fac-[ReI(CO)3(dcbpy)­(cpy)]­OTf·0.5Me2CO, fac-ReICl­(CO)3(bcpbpy)·0.5PhMe, and fac-[ReI(CO)3(bcpbpy)­(MeCN)]­OTf·MeCN. Cyclic voltammetry reveals irreversible ReII/I processes in all cases, while the trimetallic compounds show a reversible two-electron RuIII/II oxidation wave. Ligand-based reductions are generally irreversible, but reversible waves are observed for the dcbpy complexes. Electronic absorption spectra show strong d → π* metal-to-ligand charge-transfer (MLCT) and intraligand π → π* absorptions. The RuII-based MLCT bands have lower energies and higher intensities than the ReI-based ones. The monometallic species emit weakly in the red/NIR region (λem = 594–732 nm; ϕ = 0.6–8.1%) when excited at 350–520 nm. Molecular first hyperpolarizabilities β for the trimetallic complex salts are measured in MeCN solutions via the hyper-Rayleigh scattering technique at 1064 nm. Stark (electroabsorption) spectroscopic studies on the low-energy MLCT bands in frozen PrCN allow the indirect estimation of static first hyperpolarizabilities β0. The trimetallic complexes have relatively large β0 values, ca. 500 × 10–30 esu or more, which are substantially greater than those of the monometallic species.

In Vitro Anticancer Activity and in Vivo Biodistribution of Rhenium(I) Tricarbonyl Aqua Complexes

“…The structures of compounds 9 -NO 3 and 11 reveal direct coordination of the nitrate and triflate counterions to the rhenium center, whereas 10 -BF 4 and 13 display coordination of the solvent (acetonitrile and water, respectively). The direct coordination of a nitrate counterion to related rhenium tricarbonyl diimine complexes is a rare occurrence, as only three such structures are reported; , coordination of triflate and acetonitrile is a more common phenomenon. − The nature of the axial ligand appears to have a minor influence on the overall interatomic distances of the complexes, as no statistically significant differences are observed.…”

Excited-State Switching in Rhenium(I) Bipyridyl Complexes with Donor–Donor and Donor–Acceptor Substituents

“…Inorganic donor–acceptor (DA) systems based around diimine ligands have been extensively studied due to being electronically and structurally diverse, with interesting and complex behaviors. − This can be achieved by modification of the ligand or metal center, with metals such as Ru­(II), Os­(II), , Re­(I), , and Cu­(I) having been utilized. One system of particular interest is Re­(CO) 3 (NN)­X, where NN is a diimine ligand such as 2,2′-bipyridine (bpy), − 1,10-phenanthroline (phen), − or dipyrido­[3,2-a:2′,3′-c]­phenazine (dppz). − …”

ReI Tricarbonyl Complexes as Coordinate Covalent Inhibitors for the SARS‐CoV‐2 Main Cysteine Protease

“…The molecular structure of several Re I tricarbonyl complexes was determined by single‐crystal X‐ray diffraction. The structures 1 , [38, 39] 6 , [40] 7 , [41, 42] 10 , [43] 11 , [40] 17 , [44] 18 , [45] 20 , [46] 27 , [47] and 32 [47] have already been reported. The structures of compounds, 3 , 8 , 13 , 14 , 15 , 19 , 22 , 37 , and 42 are reported here (Figure 3, Table S2–S4).…”