Mono‐, Di‐, Tri‐ and Tetranuclear Rare Earth Complexes Obtained Using a Moderately Bulky Aryloxide Ligand

Redox transmetallation ligand exchange reactions involving a rare earth metal, 2,4,6‐trimethylphenol (HOmes), and a diarylmercurial afford rare earth aryloxo complexes, which are structurally characterized. Both the lanthanoid contraction and the identity of the reaction solvent are found to influence the outcome of the reactions. Using THF in the reaction affords a dinuclear species [Ln₂(Omes)₆(thf)₄]?2THF (Ln=La 1 , Nd 2 ) for the lighter rare earth metals, while a mononuclear species [Ln(Omes)₃(thf)₃] (Ln=Sm 3 , Tb 5 , Er 6 , Yb 7 , Y 8 ) is obtained for the heavier rare earth elements. Surprisingly, there is no change in metal coordination number between the two structural motifs. A divalent trinuclear linear complex [Eu₃(Omes)₆(thf)₆] 4 is obtained for Eu, and features solely bridging aryloxide ligands. Using DME as the reaction solvent affords [La(Omes)₃(dme)₂] 9 from the reaction mixture, and [Ln₂(Omes)₆(dme)₂]?PhMe (La 10 , Nd 11 ) and [Y(Omes)₃(dme)₂] 14 following crystallization of the crude product from toluene. The dinuclear species [Eu₂(Omes)₄(dme)₄] 12 contains two unidentate and two chelating DME ligands, and contrasts the linear structure of 4 . Treatment of HOmes and HgPh₂ with Yb metal in DME affords the mixed valent Yb^II/III complex [Yb₂(Omes)₅(dme)₂] 13 , which is stabilized by an intramolecular π‐Ph–Yb interaction, and is a rare example of a mixed valent rare earth aryloxide. Treatment of Er metal with HOmes at elevated temperature (solvent free) affords the homoleptic [Er₄(Omes)₁₂] 15 , which consists of a tetranuclear array of Er atoms arranged in a ‘herringbone’ fashion; the structure is stabilized by intramolecular π‐Ph–Er interactions. Reaction of La metal with HOmes under similar conditions yields toluene insoluble “La(Omes)₃”, which affords 1 following extraction with THF.     

Metal–π Interactions Dominate in the Solid‐State Structures of Molecular Heterobimetallic Alkali‐Metal–Europium(II) Aryloxo Complexes

Treatment of Eu metal, 2,6‐diphenylphenol (HOdpp), and MOdpp (M=Na, K) at elevated temperature in the presence of mercury afforded heterobimetallic complexes which were structurally characterized after crystallization from toluene. The structures of [MEu(Odpp)₃]?nPhMe (M=Na, n=1, 1 ; K, n=2.5, 2 ) consist solely of bridging aryloxide ligands and feature extensive π‐Ph–metal interactions. Rather than a heterobimetallic species, treatment of Eu metal and HOdpp with LiOdpp under similar conditions afforded a number of products, including a mixed‐valent europium complex, [Eu₂(Odpp)₃][Eu(Odpp)₄]?4 PhMe ( 3 ). The structural framework of the [Eu₂(Odpp)₃]⁺ cation of 3 is similar to that of the molecular heterobimetallics 1 and 2 , including the presence of π‐Ph–Eu interactions. The reluctance of the reaction to provide a Eu/Li heterobimetallic complex was exemplified by the simultaneous crystallization of [Eu₂(Odpp)₄]?PhMe ( 6 ) and the homoleptic cubane [Li₄(Odpp)₄]?2 C₆H₁₄ ( 5 ) from toluene/hexane.     

Melting point suppression in new lanthanoid(III) ionic liquids by trapping of kinetic polymorphs: an in situ synchrotron powder diffraction study

The complexes (N(4444))(3)[Ln(dcnm)(6)] (Ln = La-Nd, Sm; N(4444) = tetrabutylammonium) display a decrease in the melting point upon fast cooling from a melt, which is shown by in situ synchrotron based X-ray powder diffraction to be due to the formation of a second, less thermodynamically stable, polymorph.     

The effects of light lanthanoid elements (La, Ce, Nd) on (Ar)CF-Ln coordination and C-F activation in N,N-dialkyl-N'-2,3,5,6-tetrafluorophenylethane-1,2-diaminate complexes

A new class of homoleptic organoamido rare earth complexes [Ln(L(Me) or L(Et))(3)] (Ln = La, Ce, Nd; L(Me/Et) = p-HC(6)F(4)N(CH(2))(2)NMe(2)/Et(2)) exhibiting (Ar)CF-Ln interactions has been isolated from redox-transmetallation/protolysis (RTP) reactions between the free metals, Hg(C(6)F(5))(2) and L(Me/Et)H in tetrahydrofuran, together with low yields of [Ln(L(Me))(2)F](3) (Ln = La, Ce) or [Nd(L(Et))(2)F](2) species, resulting from C-F activation reactions. The structures of the homoleptic complexes have eight-coordinate Ln metals with two tridentate (N,N',F) amide ligands including (Ar)CF-Ln bonds and either a bidentate (N,F) ligand (Ln = La, Ce, Nd; L(Et)) or a bidentate (N,N') ligand (Ln = Nd; L(Me)), in an unusual case of linkage variation. All (Ar)CF-Ln bond lengths are shorter than or similar to the corresponding Ln-NMe(2)/Et(2) bond lengths. In [Ln(L(Me))(2)F](3) (Ln = La, Ce) complexes, there is a six-membered ring framework with alternating F and Ln atoms and the metal atoms are eight-coordinate with two tridentate (N,N',F) L(Me) ligands, whilst [Nd(L(Et))(2)F](2) is a fluoride-bridged dimer.     

Lanthanoid-based ionic liquids incorporating the dicyanonitrosomethanide anion

A series of low-melting-point salts with hexakisdicyanonitrosomethanidolanthanoidate anions has been synthesised and characterised: (C(2) mim)(3) [Ln(dcnm)(6)] (1?Ln; 1?Ln=1?La, 1?Ce, 1?Pr, 1?Nd), (C(2) C(1) mim)(3) [Pr(dcnm)(6)] (2?Pr), (C(4) C(1) pyr)(3) [Ce(dcnm)(6)] (3?Ce), (N(1114))(3) [Ln(dcnm)(6)] (4?Ln; 4?Ln=4?La, 4?Ce, 4?Pr, 4?Nd, 4?Sm, 4?Gd), and (N(1112OH) )(3) [Ce(dcnm)(6)] (5?Ce) (C(2) mim=1-ethyl-3-methylimidazolium, C(2) C(1) mim=1-ethyl-2,3-dimethylimidazolium, C(4) C(1) py=N-butyl-4-methylpyridinium, N(1114) =butyltrimethylammonium, N(1112OH) =2-(hydroxyethyl)trimethylammonium=choline). X-ray crystallography was used to determine the structures of complexes 1?La, 2?Pr, and 5?Ce, all of which contain [Ln(dcnm)(6)](3-) ions. Complexes 1?Ln and 2?Pr were all ionic liquids (ILs), with complex 3?Ce melting at 38.1?°C, the lowest melting point of any known complex containing the [Ln(dcnm)(6)](3-) trianion. The ammonium-based cations proved to be less suitable for forming ILs, with complexes 4?Sm and 4?Gd being the only salts with the N(1114) cation to have melting points below 100?°C. The choline-containing complex 5?Ce did not melt up to 160?°C, with the increase in melting point possibly being due to extensive hydrogen bonding, which could be inferred from the crystal structure of the complex.     

Cell Uptake and Trafficking Behavior of Non‐covalent,Coiled‐coil Based Polymer–Drug Conjugates

This paper reports on the cell uptake and trafficking properties of a series of non‐covalent polymer–drug conjugates. These nanomedicines are composed of a poly(N‐(2‐hydroxypropyl)methacrylamide) backbone functionalized with multiple copies of a drug. The drug moieties are attached to the polymer via a non‐covalent, so called coiled coil motif, which is formed by heterodimerization of two complementary peptide strands, one of which is attached to the polymer carrier and the other to the drug. Cytotoxicity and FACS experiments, which were carried out with model anticancer drug or fluorophore conjugates, provided insight into the cell uptake and trafficking behavior of these conjugates.

     

Improved syntheses of Ru(CO)2 (O3SCF3)2 (bidentate) complexes and their conversion into new [Ru(CO)2 (bidentate)2]2+ complexes

Reaction of the complexes Ru(CO)₂Cl₂L [L = 2,2′-bipyridyl (bpy) or 1,10-phenanthroline (phen)] with trifluoromethanesulphonic acid under carefully controlled conditions yields Ru[cis-(CO)₂] [cis-(O₃SCF₃)₂] (bidentate complexes. From reactions of the trifluoromethanesulphonates with the appropriate bidentate ligands, the new complexes [cis-Ru(CO)₂-L(L′)]²⁺ (L as above; L′ = 4,4′-dimethyl-2,2′-bipyridyl or 4,4′-diisopropyl-2,2′-bipyridyl) as well as the known [_cis-Ru(CO)₂L₂]²⁺ and [cis-Ru(CO)₂bpy(phen)]²⁺ have been prepared.