Unsymmetrical Metallosupramolecular Polycondensation of Expanded l-Amino Acid Containing Platinum(II) Complex in Nonpolar Solvents

Abstract

The construction of a well-designed three-dimensional structure is promising for the development of artificial enzymes with outstanding functions. A combination of chiral polypeptides and metallosupramolecular polymers is a promising candidate for this purpose. An expanded L-amino acid containing platinum(II) complex was designed and unsymmetrically polymerized via metallosupramolecular polycondensation in nonpolar solvents. The resulting expanded polypeptide was analyzed through 1 H NMR spectroscopy, circular dichroism (CD), and theoretical calculations accompanied by X-ray analysis of a model compound and elementary reactions. The molar mass of the polymer was estimated through end-group analysis and 1 H diffusionordered NMR spectroscopy (DOSY). The DOSY spectra demonstrate that at least 17-mer is present in chloroform. The CD spectra reflect the local structure of the monomer unit and suggest the presence of two conformers in a dynamic equilibrium. The entire structure of the polymer is considered to be a fluctuating mixture of chiral helices. The synthetic procedure in this study will be applied to construct chiral molecular architectures leading functional polymer materials.

Synthesis of Expanded Poly(l-amino acid) Containing Phenylethynyl(terpyridine)platinum(II) Moieties

“…The other absorption bands were assigned to transitions in a local unit. Because the major absorption bands are attributed to local transitions, the shape of the CD spectra does not significantly influence the conformation of the polymer, which differs from previous research . Therefore, geometrically optimized structures were used to estimate the solution structure of the polymer.…”

“…The structure of poly-1 is a right-handed 7/2 helix with a 63 Å pitch and 19 Å diameter, whereas poly-2 forms a right-handed 4/1 helix with a 47 Å pitch and 28 Å diameter. The secondary structure of the expanded poly( l -amino acid) significantly depended on the side chains, which is consistent with previous studies. − , …”

“…The secondary structure of the expanded poly(L-amino acid) significantly depended on the side chains, which is consistent with previous studies. [25][26][27]45 ■ CONCLUSIONS Expanded poly(L-leucine) (poly-1) and poly(L-valine) (poly-2) containing phenylethynyl(terpyridine)platinum(II) moieties in the main chain were successfully synthesized through the copper-catalyzed formation of robust platinum−acetylide bonds. The coordinate bonds were retained even in polar solvents, such as DMSO.…”

“…Here, the polymerization proceeds through the formation of covalent amide bonds by conventional condensation methods used in general peptide synthesis . When an unsymmetrical unit with tridentate and monodentate ligands was used, unsymmetrical metallosupramolecular polycondensation − afforded expanded poly­( l -amino acid) containing platinum­(II) complexes in nonpolar solvents . The selected monodentate pyridine ligand is easily replaced with the originally coordinated dimethyl sulfoxide (DMSO) ligand to proceed with polymerization; however, the resulting Pt–N bond is cleaved by polar solvents; therefore, nonpolar solvents are necessary.…”

C–H Metalation of Terpyridine Stereoisomers with Ni(II), Pd(II), and Pt(II)

“…Double NˆCˆC cyclometalation with dianionic NˆCˆC 2− ligands based on diphenyl-2-pyridine (Hdphpy) was never observed for Pt(II), while for Pd(II) and Ni(II), the complexes [M(dphpy)(PPh 3 )] (M = Pd and Ni) were recently reported [56]. In contrast to this, − CˆNˆC − coordination with the prototypical 2,6-diphenylpyridine system (Hdpp) to Pt(II) is quite frequent [57][58][59][60][61][62], while for Pd(II) the first example was only very recently reported [Pd(dpp)(PPh 3 )] [63], and no Ni(II) derivatives have been found. Triple CˆCˆC cyclometalation is not known for any of these metals.…”