Tuning of Supramolecular Architectures of l-Valine-Containing Dicyanoplatinum(II) 2,2'-Bipyridine Complexes by Metal-Metal, π-π Stacking, and Hydrogen-Bonding Interactions.

A series of newly synthesized dicyanoplatinum(II) 2,2'-bipyridine complexes exhibits self-assembly properties in solution after the incorporation of the l-valine amino units appended with various hydrophobic motifs. These l-valine-derived substituents were found to have critical control over the aggregation behaviors of the complexes in the solution state. On one hand, one of the complexes was found to exhibit interesting circularly polarized luminescence (CPL) signals at low temperature due to the formation of chiral spherical aggregates in the temperature-dependent studies. On the other hand, systematic transformation from less uniform aggregates to well-defined fibrous and rod-like structures via Pt⋅⋅⋅Pt and π-π stacking interactions has also been observed in the mixed-solvent studies. These changes were monitored by UV/Vis absorption, emission, circular dichroism (CD), and CPL spectroscopies, and morphologies were studied by electron microscopy.

[1]  V. Yam,et al.  NIR-emissive alkynylplatinum(II) terpyridyl complex as a turn-on selective probe for heparin quantification by induced helical self-assembly behaviour. , 2011, Chemistry.

[2]  V. Miskowski,et al.  Electronic Spectroscopy of Chloro(terpyridine)platinum(II) , 1995 .

[3]  V. Yam,et al.  Polymer-induced self-assembly of alkynylplatinum(II) terpyridyl complexes by metal...metal/pi...pi interactions. , 2005, Angewandte Chemie.

[4]  V. Miskowski,et al.  The effect of linear chain structure on the electronic structure of pt(II) diimine complexes , 1991 .

[5]  V. Yam,et al.  Solvent-induced aggregation through metal...metal/pi...pi interactions: large solvatochromism of luminescent organoplatinum(II) terpyridyl complexes. , 2002, Journal of the American Chemical Society.

[6]  B. Shaw,et al.  Bimetallic systems. Part 7. Platinum and palladium dicyanides containing terminal or bridging Ph2PCH2PPh2 and heterobimetallics with silver, gold, mercury, rhodium, iridium, or molybdenum , 1985 .

[7]  C. Chung,et al.  Dual pH- and temperature-responsive metallosupramolecular block copolymers with tunable critical micelle temperature by modulation of the self-assembly of NIR-emissive alkynylplatinum(II) Complexes induced by changes in hydrophilicity and electrostatic effects. , 2013, Chemistry.

[8]  C. Che,et al.  Luminescent platinum(II) complexes. Electronic spectroscopy of platinum(II) complexes of 2,2′:6′,2″-terpyridine (terpy) and p-substituted phenylterpyridines and crystal structure of [Pt(terpy)CI][CF3SO3] , 1993 .

[9]  C. Che,et al.  Solid-state emission of dicyanoplatinum(II) and -palladium(II) complexes of substituted 2,2'-bipyridines and 1,10-phenanthroline and x-ray crystal structures of isomorphous M(bpy)(CN)2 (bpy = 2,2'-bipyridine; M = Pt, Pd) , 1989 .

[10]  K. R. Mann,et al.  “Vapochromic” Compounds as Environmental Sensors. 2. Synthesis and Near-Infrared and Infrared Spectroscopy Studies of [Pt(arylisocyanide)4][Pt(CN)4] upon Exposure to Volatile Organic Compound Vapors , 1997 .

[11]  V. Yam,et al.  Dynamic scaffold of chiral binaphthol derivatives with the alkynylplatinum(II) terpyridine moiety , 2013, Proceedings of the National Academy of Sciences.

[12]  C. Che,et al.  Spectroscopy and x-ray crystal structure of luminescent bis[bis(diphenylphosphino)methane]tetracyanodiplatinum , 1989 .

[13]  H. Gray,et al.  Pyrophosphito-bridged diplatinum chemistry , 1989 .

[14]  V. Miskowski,et al.  Electronic spectra and photophysics of platinum(II) complexes with alpha-diimine ligands - Solid-state effects. I - Monomers and ligand pi dimers , 1989 .

[15]  J. Field,et al.  Luminescence properties of salts of the [Pt(4′Ph-terpy)Cl]+ chromophore: crystal structure of the red form of [Pt(4′Ph-terpy)Cl]BF4 (4′Ph-terpy = 4′-phenyl-2,2′∶6′,2″-terpyridine) , 1999 .

[16]  A. Vogler,et al.  Photoluminescence of platinum complex [PtII(4,7-diphenyl-1,10-phenanthroline)(CN)2] in solution , 1990 .

[17]  Zhifeng Liu,et al.  Head-to-tail dimerization and organogelating properties of click peptidomimetics. , 2012, Organic letters.

[18]  V. Yam,et al.  Single-stranded nucleic acid-induced helical self-assembly of alkynylplatinum(II) terpyridyl complexes , 2006, Proceedings of the National Academy of Sciences.

[19]  C. Che,et al.  Spectroscopic Properties of Luminescent Platinum(II) Complexes Containing 4,4‘,4‘ ‘-Tri-tert-butyl-2,2‘:6‘,2‘ ‘-terpyridine (tBu3tpy). Crystal Structures of [Pt(tBu3tpy)Cl]ClO4 and [Pt(tBu3tpy){CH2C(O)Me}]ClO4 , 1999 .

[20]  S. Lippard,et al.  Metallointercalation reagents. 2-hydroxyethanethiolato(2,2',2'-terpyridine)-platinum(II) monocation binds strongly to DNA by intercalation. , 1974, Proceedings of the National Academy of Sciences of the United States of America.

[21]  P. Vierling,et al.  Synthesis of new amphiphilic perfluoroalkylated bipyridines , 1992 .

[22]  V. Miskowski,et al.  Lowest electronic excited states of platinum(II) diimine complexes. , 2000, Inorganic chemistry.

[23]  J. Stendahl,et al.  Intermolecular Forces in the Self‐Assembly of Peptide Amphiphile Nanofibers , 2006 .

[24]  H. Cui,et al.  Supramolecular Polymers Formed by ABC Miktoarm Star Peptides. , 2013, ACS macro letters.

[25]  V. Yam,et al.  A platinum(II) terpyridine metallogel with an L-valine-modified alkynyl ligand: interplay of Pt⋅⋅⋅Pt, π-π and hydrogen-bonding interactions. , 2013, Chemistry.

[26]  R. P. Tang,et al.  Synthesis, Luminescence, Electrochemistry, and Ion-Binding Studies of Platinum(II) Terpyridyl Acetylide Complexes , 2001 .

[27]  Vonika Ka-Man Au,et al.  Light-Emitting Self-Assembled Materials Based on d(8) and d(10) Transition Metal Complexes. , 2015, Chemical reviews.

[28]  V. Yam,et al.  Influence of counteranion on the chiral supramolecular assembly of alkynylplatinum(II) terpyridyl metallogels that are stabilised by Pt...Pt and pi-pi interactions. , 2009, Chemistry.

[29]  M. Zabel,et al.  Spectroscopic studies of cyclometalated platinum(II) complexes : superposition of two different spectroscopic species in the electronic spectra of a single crystal of [Pt(bpm)(CN)2] (bpm = 2,2'-bipyrimidine) , 1990 .

[30]  T. Hirao,et al.  Highly ordered structures of peptides by using molecular scaffolds. , 2004, Chemical Society reviews.

[31]  E. W. Meijer,et al.  About Supramolecular Assemblies of π-Conjugated Systems , 2005 .

[32]  V. Yam,et al.  Luminescent dinuclear platinum(II) terpyridine complexes with a flexible bridge and "sticky ends". , 2006, Angewandte Chemie.

[33]  Kirandeep K. Deol,et al.  Straightforward access to mono- and bis-cycloplatinated helicenes displaying circularly polarized phosphorescence by using crystallization resolution methods , 2014 .

[34]  M. Croft,et al.  Origin of Polychromism of Cis Square-Planar Platinum(II) Complexes: Comparison of Two Forms of [Pt(2,2'-bpy)(Cl2] , 1994 .

[35]  V. Yam,et al.  Supramolecular self-assembly of amphiphilic anionic platinum(II) complexes: a correlation between spectroscopic and morphological properties. , 2011, Journal of the American Chemical Society.

[36]  V. Yam,et al.  Functionalized platinum(II) terpyridyl alkynyl complexes as colorimetric and luminescence pH sensors. , 2005, Inorganic chemistry.

[37]  D. Roundhill,et al.  Triplet excited-state chemistry of diplatinum(II) complexes: comparative spectroscopy and quenching rate constants between the tetrakis(.mu.-pyrophosphito)diplatinate(II) and the tetrakis[.mu.-methylenebis(phosphonito)]diplatinate(II) tetraanions , 1988 .

[38]  A. Kobayashi,et al.  Vapour‐Induced Amorphous–Crystalline Transformation of a Luminescent Platinum(II)–Diimine Complex , 2010 .

[39]  A. Shanzer,et al.  Photoinduced Electron Transfer in Ruthenium Bipyridyl Complexes: Evidence for the Existence of a Cage with Molecular Oxygen , 2004 .

[40]  Masako Kato,et al.  Vapochromism and Crystal Structures of Luminescent Dicyano(2,2′-Bipyridine)Platinum(II) , 2002 .

[41]  Richard Eisenberg,et al.  Vapochromism and its structural basis in a luminescent Pt(II) terpyridine-nicotinamide complex. , 2004, Journal of the American Chemical Society.

[42]  S. Stupp,et al.  Tunable mechanics of peptide nanofiber gels. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[43]  Jean-Marie Lehn,et al.  Toward Self-Organization and Complex Matter , 2002, Science.

[44]  Samuel I Stupp,et al.  Switching of Self-Assembly in a Peptide Nanostructure with a Specific Enzyme. , 2011, Soft matter.

[45]  K. R. Mann,et al.  Inclusion of Organic Vapors by Crystalline, Solvatochromic [Pt(aryl isonitrile)4][Pd(CN)4] Compounds. “Vapochromic” Environmental Sensors , 1995 .

[46]  R. Gillard,et al.  Spectroscopic studies on some compounds (including dimorphic solids) of platinum(II) with 2,2′-bipyridyl and its analogues , 1975 .

[47]  S. Stupp,et al.  Tuning supramolecular rigidity of peptide fibers through molecular structure. , 2010, Journal of the American Chemical Society.

[48]  R. E. Marsh,et al.  A revision of the structure of (bipyridyl-N,N')-dicyanoplatinum(II) , 1996 .

[49]  K. R. Mann,et al.  A Vapochromic LED , 1998 .

[50]  Wei Huang,et al.  Potential Switchable Circularly Polarized Luminescence from Chiral Cyclometalated Platinum(II) Complexes , 2014, Inorganic chemistry.

[51]  Jean-Marie Lehn,et al.  Supramolecular Chemistry: Concepts And Perspectives , 2014 .

[52]  V. Miskowski,et al.  Electronic spectra and photophysics of platinum(II) complexes with .alpha.-diimine ligands solid-state effects. 2. Metal-metal interaction in double salts and linear chains , 1991 .

[53]  Hong-Xing Zhang,et al.  Theoretical insight into electronic structures and spectroscopic properties of [Pt2(pop)4]4-, [Pt2(pcp)4]4-, and related derivatives (pop = P2O5H2(2-) and pcp = P2O4CH4(2-)). , 2006, Inorganic chemistry.

[54]  E. W. Meijer,et al.  Functional Supramolecular Polymers , 2012, Science.

[55]  S. Stupp,et al.  PAPER www.rsc.org/softmatter | Soft Matter The internal structure of self-assembled peptide amphiphiles nanofibers{ , 2007 .

[56]  D. Roundhill,et al.  Synthesis structure and spectroscopy of the diplatinum(II) complex Pt2(pcp)44-, a Pt2(pop)44- analog having methylenebisphosphinic acid bridges , 1986 .

[57]  B. Tang,et al.  Chiral poly(4-ethynylbenzoyl-l-valine)-induced helical self-assembly of alkynylplatinum(II) terpyridyl complexes with tunable electronic absorption, emission, and circular dichroism changes. , 2009, Chemistry.

[58]  G. Arena,et al.  Synthesis, Characterization, Absorption Spectra, and Luminescence Properties of Organometallic Platinum(II) Terpyridine Complexes. , 1998, Inorganic chemistry.

[59]  G. Cheng,et al.  Highly phosphorescent platinum(ii) emitters: photophysics, materials and biological applications , 2016, Chemical science.

[60]  K. K. Lo,et al.  Induced self-assembly and disassembly of water-soluble alkynylplatinum(II) terpyridyl complexes with “switchable” near-infrared (NIR) emission modulated by metal–metal interactions over physiological pH: demonstration of pH-responsive NIR luminescent probes in cell-imaging studies , 2013 .

[61]  Guoxin Wang,et al.  Luminescent alkynylplatinum(II) terpyridyl metallogels stabilized by Pt...Pt, pi-pi, and hydrophobic-hydrophobic interactions. , 2009, Langmuir : the ACS journal of surfaces and colloids.

[62]  V. Yam,et al.  Self-assembly of luminescent alkynylplatinum(II) terpyridyl complexes: modulation of photophysical properties through aggregation behavior. , 2011, Accounts of chemical research.

[63]  S. Noro,et al.  Vapour-adsorption and chromic behaviours of luminescent coordination polymers composed of a Pt(II)-diimine metalloligand and alkaline-earth metal ions. , 2011, Dalton transactions.

[64]  T. Kawai,et al.  Circularly Polarized Luminescence in Chiral Aggregates: Dependence of Morphology on Luminescence Dissymmetry. , 2014, The journal of physical chemistry letters.

[65]  W. Schaefer,et al.  Linear-Chain Structures of Platinum(II) Diimine Complexes , 1997 .

[66]  A. Vogler,et al.  Luminescent excimers and exciplexes of PtII compounds , 1998 .

[67]  M. Hasegawa,et al.  Outstanding Vapochromism and pH-dependent Coloration of Dicyano(4,4′-dicarboxy-2,2′-bipyridine)platinum(II) with a Three-dimensional Network Structure , 2005 .

[68]  S. Stupp,et al.  Aqueous self-assembly of unsymmetric Peptide bolaamphiphiles into nanofibers with hydrophilic cores and surfaces. , 2003, Journal of the American Chemical Society.

[69]  T. Kawai,et al.  Novel helical assembly of a Pt(II) phenylbipyridine complex directed by metal-metal interaction and aggregation-induced circularly polarized emission. , 2015, Dalton transactions.

[70]  S. Noro,et al.  Multifunctional sensing ability of a new Pt/Zn-based luminescent coordination polymer. , 2010, Dalton transactions.

[71]  D. McMillin,et al.  Studies of the Room-Temperature Absorption and Emission Spectra of [Pt(trpy)X]+ Systems , 1994 .

[72]  V. Yam,et al.  Hierarchical helices of helices directed by Pt⋯Pt and π–π stacking interactions: reciprocal association of multiple helices of dinuclear alkynylplatinum(ii) complex with luminescence enhancement behavior , 2013 .

[73]  C. Che,et al.  Inorganic excimer. Spectroscopy, photoredox properties and excimeric emission of dicyano(4,4′-di-tert-butyl-2,2′-bipyridine)platinum(II) , 1991 .

[74]  S. Stupp,et al.  Coassembly of amphiphiles with opposite peptide polarities into nanofibers. , 2005, Journal of the American Chemical Society.

[75]  Yingli An,et al.  Chiral Micelles of Achiral TPPS and Diblock Copolymer Induced by Amino Acids , 2009 .

[76]  Guoxin Wang,et al.  Luminescent metallogels of platinum(II) terpyridyl complexes: interplay of metal...metal, pi-pi and hydrophobic-hydrophobic interactions on gel formation. , 2007, Chemical communications.

[77]  C. Che,et al.  Novel luminescent platinum(II) complexes. Photophysics and photochemistry of Pt(5,5′-Me2bpy)(CN)2(5,5′-Me2bpy=5,5′-dimethyl-2,2′-bipyridine) , 1989 .

[78]  Ibrahim Eryazici,et al.  Square-planar Pd(II), Pt(II), and Au(III) terpyridine complexes: their syntheses, physical properties, supramolecular constructs, and biomedical activities. , 2008, Chemical reviews.