Supramolecular ssDNA templated porphyrin and metalloporphyrin nanoassemblies with tunable helicity.
Free-base and nickel porphyrin-diaminopurine conjugates were formed by hydrogen-bond directed assembly on single-stranded oligothymidine templates of different lengths into helical multiporphyrin nanoassemblies with highly modular structural and chiroptical properties. Large red-shifts of the Soret band in the UV/Vis spectroscopy confirmed strong electronic coupling among assembled porphyrin-diaminopurine units. Slow annealing rates yielded preferentially right-handed nanostructures, whereas fast annealing yielded left-handed nanostructures. Time-dependent DFT simulations of UV/Vis and CD spectra for model porphyrin clusters templated on the canonical B-DNA and its enantiomeric form, were employed to confirm the origin of observed chiroptical properties and to assign the helicity of porphyrin nanoassemblies. Molar CD and CD anisotropy g factors of dialyzed templated porphyrin nanoassemblies showed very high chiroptical anisotropy. The DNA-templated porphyrin nanoassemblies displayed high thermal and pH stability. The structure and handedness of all assemblies was preserved at temperatures up to +85 °C and pH between 3 and 12. High-resolution transition electron microscopy confirmed formation of DNA-templated nickel(II) porphyrin nanoassemblies and their self-assembly into helical fibrils with micrometer lengths.
Department of Chemistry, University of Wyoming, 1000 E. University Avenue, Laramie, WY 82071 (USA), Fax: (+1) 307-766-2807.
Gevorg
G
Sargsyan
Brian M
BM
Leonard
Jan
J
Kubelka
Milan
M
Balaz
D002942:Circular Dichroism; D059371:DNA, B-Form / Q000737:chemistry; D004277:DNA, Single-Stranded / Q000737:chemistry*; D006860:Hydrogen Bonding; D008665:Metalloporphyrins / Q000737:chemistry*; D008958:Models, Molecular; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D009532:Nickel / Q000737:chemistry; D009690:Nucleic Acid Conformation; D011166:Porphyrins / Q000737:chemistry*; D013237:Stereoisomerism
D059371:DNA, B-Form; D004277:DNA, Single-Stranded; D008665:Metalloporphyrins; D011166:Porphyrins; D009532:Nickel
TDDFT calculations; circular dichroism; porphyrins; self-assembly; supramolecular chemistry