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Synthesis and Complexation of a Free Germanide Bearing a Tridentate N-Heterocyclic Substituent.

ABSTRACT: The tris-N-heterocycle germanide (tmim)Ge- (1) (tmimH3 = tris(3-methylindol-2-yl)methane) was synthesized by nucleophilic substitution for the tmim3- trianion on GeCl2·dioxane. In combination with the previously reported (tmim)Si- and (tmim)P analogues, it provides a convenient model for investigating the influence of the central atom on the properties of isoelectronic ligands. Complexation of the germanide (tmim)Ge- to CuCl resulted in the dimeric chloro cuprate [(tmim)GeCu(?-Cl)]2 2-, which is prone to dissociation in MeCN to form the neutral, solvated germylcopper (tmim)GeCu(NCMe)3. The reaction of 1 with Fe2(CO)9 afforded the germyl iron tetracarbonyl [(tmim)GeFe(CO)4]-. Analysis of the ??(CO) infrared absorption bands in this complex indicates that the combined electron donating and accepting properties of 1 are found in between those of (tmim)P and (tmim)Si-. In contrast to (tmim)Si-, (tmim)Ge- is reluctant to coordinate to FeCl2, likely because of its softer Lewis base character. Key structural features of the ligands and complexes reflect changes in their electronic properties. In particular, the N-Ge-N angles increase upon coordination to a metal fragment, suggesting increasing hybridization of the Ge s- and p-orbitals. These findings will be useful in further understanding low-valent heavier group 14 complexes in organometallic chemistry.

SUBMITTER: Witteman L

PROVIDER: S-EPMC6354728 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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Synthesis and Complexation of a Free Germanide Bearing a Tridentate N-Heterocyclic Substituent.

Witteman Léon L van Beek Cody B CB van Veenhuizen Oscar N ON Lutz Martin M Moret Marc-Etienne ME

Organometallics 20190109 2

The tris-N-heterocycle germanide (tmim)Ge- (1) (tmimH3 = tris(3-methylindol-2-yl)methane) was synthesized by nucleophilic substitution for the tmim3- trianion on GeCl2·dioxane. In combination with the previously reported (tmim)Si- and (tmim)P analogues, it provides a convenient model for investigating the influence of the central atom on the properties of isoelectronic ligands. Complexation of the germanide (tmim)Ge- to CuC ...[more]

PMID: 30713362

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Project description:The synthesis, photophysics, and photobiological activities of a series of novel neutral heteroleptic cyclometalated iridium(iii) complexes incorporating boron dipyrromethene (BODIPY) substituted N-heterocyclic carbene (NHC) ligands (Ir1-Ir5) are reported. The effect of the substitution position of BODIPY on the NHC ligands, either on C4 of the phenyl ring (Ir1-Ir3) or C5 of the benzimidazole unit (Ir4 and Ir5), and its linker type (single or triple bond) on the photophysical properties was studied. Ir1-Ir5 exhibited BODIPY-localized intense 1IL (intraligand transition)/1MLCT (metal-to-ligand charge transfer) absorption at 530-543 nm and 1,3IL/1,3CT (charge transfer) emission at 582-610 nm. The nanosecond transient absorption results revealed that the lowest triplet excited states of these complexes were the BODIPY-localized 3?,?* states. Complexes Ir4 and Ir5 exhibited blue-shifted 1IL absorption and 1,3IL/1,3CT emission bands compared to the corresponding absorption and emission bands in complexes Ir1 and Ir3. However, replacing the methyl substituents on N3 of benzimidazole in complexes Ir1 and Ir4 with oligoether substituents in Ir3 and Ir5, respectively, did not impact the energies of the low-energy absorption and emission bands in the corresponding complexes. Water-soluble complexes Ir3 and Ir5 have been explored as photosensitizers for in vitro photodynamic therapy (PDT) effects toward human SKMEL28 melanoma cells. Ir3 showed no dark cytotoxicity (EC50 > 300 ?M) but good photocytotoxic activity (9.66 ± 0.28 ?M), whereas Ir5 exhibited a higher dark cytotoxicity (20.2 ± 1.26 ?M) and excellent photocytotoxicity (0.15 ± 0.01 ?M). The phototherapeutic indices with visible light (400-700 nm) activation were >31 for Ir3 and 135 for Ir5. Ir3 and Ir5 displayed 1O2 quantum yields of 38% and 22% in CH3CN, respectively, upon 450 nm excitation. Ir5 was more effective at generating reactive oxygen species (ROS) in vitro. Ir5 was also active against Staphylococcus aureus upon visible light activation, with a phototherapeutic index of >15 and EC50 value of 6.67 ?M. These photobiological activities demonstrated that these neutral Ir(iii) complexes are promising in vitro PDT reagents, and substitution at C5 on the benzimidazole group of the NHC ligand was superior to C4 substitution on the phenyl ring.

Dataset Information

Synthesis and Complexation of a Free Germanide Bearing a Tridentate N-Heterocyclic Substituent.

Publications

Synthesis and Complexation of a Free Germanide Bearing a Tridentate N-Heterocyclic Substituent.

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