Interplays of excited state structures and dynamics in copper(I) diimine complexes: Implications and perspectives

Abstract Although they were discovered almost four decades ago, Cu(I) diimine complexes have emerged as a group of transition metal complexes that can play important roles in solar energy conversion and utilization, and have potential to replace the quintessential ruthenium polypyridyl complexes as light sensitizers, electron donors and catalytic centers. This review includes some recent photophysical studies and transient structural studies of Cu(I) diimine complexes using ultrafast optical transient absorption and emission as well as X-ray transient absorption spectroscopy. The main focus is on identifying the key structural factors that influence the excited-state properties, such as structural reorganization, intersystem crossing and solvent quenching, with these relatively new techniques on the ultrafast time scales. Ultimately, these structural factors can be used to rationally control the energetics and dynamics of the MLCT state during the light conversion processes. This insight will serve as guidance for material design using Cu(I) diimine complexes as building blocks.

[1]  M. Neuburger,et al.  An element of surprise--efficient copper-functionalized dye-sensitized solar cells. , 2008, Chemical communications.

[2]  Rony S. Khnayzer,et al.  Robust cuprous phenanthroline sensitizer for solar hydrogen photocatalysis. , 2013, Journal of the American Chemical Society.

[3]  C. M. Elliott,et al.  Dye-Sensitized Solar Cell Studies of a Donor-Appended Bis(2,9-dimethyl-1,10-phenanthroline) Cu(I) Dye Paired with a Cobalt-Based Mediator , 2013 .

[4]  Xiaojing Wang,et al.  A density functional investigation of charge transfer and structural distortions of cuprous(I) bis-phenanthroline under photo-induced excitation , 2006 .

[5]  D. McMillin,et al.  A light-induced redox reaction of bis(2,9-dimethyl-1,10-phenanthroline)copper(I) , 1977 .

[6]  D. McMillin,et al.  Steric Effects in the Ground and Excited States of Cu(NN)2+ Systems , 1997 .

[7]  P. Pianetta,et al.  A short range probe for investigating metalloprotein structures: Fourier analysis of the extended x‐ray absorption fine structure , 1975 .

[8]  P. Gantzel,et al.  Effects of Sterics and Electronic Delocalization on the Photophysical, Structural, and Electrochemical Properties of 2,9-Disubstituted 1,10-Phenanthroline Copper(I) Complexes. , 1999, Inorganic chemistry.

[9]  Yongjun Yuan,et al.  A copper(I) dye-sensitised TiO2-based system for efficient light harvesting and photoconversion of CO2 into hydrocarbon fuel. , 2012, Dalton transactions.

[10]  F. Diederich,et al.  A COPPER(I)-COMPLEXED ROTAXANE WITH TWO FULLERENE STOPPERS , 1995 .

[11]  D. McMillin,et al.  Photostudies of copper(I) systems. 6. Room-temperature emission and quenching studies of bis(2,9-dimethyl-1,10-phenanthroline)copper(I) , 1980 .

[12]  D. McMillin,et al.  Photostudies of copper(I) systems. 7. Studies of bimolecular reactions involving cobalt(III) complexes, chromium(III) complexes, or oxygen following the excitation of bis(2,9-dimethyl-1,10-phenanthroline)copper(I) , 1981 .

[13]  V. Balzani,et al.  Endoreceptors with Convergent Phenanthroline Units: A Molecular Cavity for Six Guest Molecules , 1991 .

[14]  J. F. Stoddart,et al.  Highly efficient ultrafast electron injection from the singlet MLCT excited state of copper(I) diimine complexes to TiO2 nanoparticles. , 2012, Angewandte Chemie.

[15]  A. Soldatov,et al.  Application of XANES spectroscopy to study local structure of photoexcited Cu complex , 2009 .

[16]  D. McMillin,et al.  Bis(2,9-diphenyl-1,10-phenanthroline)copper(I): a copper complex with a long-lived charge-transfer excited state , 1983 .

[17]  Qisheng Zhang,et al.  Highly Efficient Green Phosphorescent Organic Light‐Emitting Diodes Based on CuI Complexes , 2004 .

[18]  N. Robertson,et al.  Neutral copper(I) dipyrrin complexes and their use as sensitizers in dye-sensitized solar cells. , 2014, Dalton transactions.

[19]  Philip Coppens,et al.  Capturing and analyzing the excited-state structure of a Cu(I) phenanthroline complex by time-resolved diffraction and theoretical calculations. , 2009, Journal of the American Chemical Society.

[20]  D. McMillin,et al.  Photoprocesses of Copper Complexes That Bind to DNA. , 1998, Chemical reviews.

[21]  M. Grätzel,et al.  A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films , 1991, Nature.

[22]  A. Listorti,et al.  Heteroleptic copper(I) complexes coupled with methano[60]fullerene: synthesis, electrochemistry, and photophysics. , 2008, Inorganic chemistry.

[23]  C. Kelly,et al.  Electron and energy transfer from CuI MLCT excited states , 1998 .

[24]  D. Gosztola,et al.  Rapid excited-state structural reorganization captured by pulsed X-rays. , 2002, Journal of the American Chemical Society.

[25]  F. Castellano,et al.  Design of a long-lifetime, earth-abundant, aqueous compatible Cu(I) photosensitizer using cooperative steric effects. , 2013, Inorganic chemistry.

[26]  Lin X. Chen,et al.  Probing transient molecular structures in photochemical processes using laser-initiated time-resolved X-ray absorption spectroscopy. , 2005, Annual review of physical chemistry.

[27]  M. Chergui,et al.  Ultrafast X-ray absorption spectroscopy. , 2004, Chemical reviews.

[28]  D. McMillin,et al.  Studies of photoinduced electron transfer from bis(2,9-dimethyl-1,10-phenanthroline)copper(I) , 1978 .

[29]  N. Armaroli.  From metal complexes to fullerene arrays: exploring the exciting world of supramolecular photochemistry fifteen years after its birth , 2003, Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology.

[30]  Lin X. Chen.  Taking snapshots of photoexcited molecules in disordered media by using pulsed synchrotron X-rays. , 2004, Angewandte Chemie.

[31]  C. Housecroft,et al.  Hole-transport functionalized copper(I) dye sensitized solar cells. , 2013, Physical chemistry chemical physics : PCCP.

[32]  G. B. Shaw,et al.  Exciplex formation of copper(II) octaethylporphyrin revealed by pulsed X-rays , 2004 .

[33]  A. Kovalevsky,et al.  Solid-state structure dependence of the molecular distortion and spectroscopic properties of the Cu(I) bis(2,9-dimethyl-1,10-phenanthroline) ion. , 2003, Inorganic chemistry.

[34]  M. Boujtita,et al.  First application of the HETPHEN concept to new heteroleptic bis(diimine) copper(I) complexes as sensitizers in dye sensitized solar cells. , 2013, Dalton transactions.

[35]  Jean-Pierre Sauvage,et al.  Transition Metal-Containing Rotaxanes and Catenanes in Motion: Toward Molecular Machines and Motors , 1998 .

[36]  A. Munkholm,et al.  Capturing a Photoexcited Molecular Structure Through Time-Domain X-ray Absorption Fine Structure , 2001, Science.

[37]  D. McMillin,et al.  Cooperative Substituent Effects on the Excited States of Copper Phenanthrolines. , 1999, Inorganic chemistry.

[38]  D. McMillin,et al.  CONCENTRATION‐DEPENDENT LIFETIMES OF Cu(NN)+2 SYSTEMS: EXCIPLEX QUENCHING FROM THE ION PAIR STATE , 1989 .

[39]  N. McClenaghan,et al.  Improving the photophysical properties of copper(I) bis(phenanthroline) complexes , 2008 .

[40]  J. V. van Lier,et al.  Ultrafast studies of the excited-state dynamics of copper and nickel phthalocyanine tetrasulfonates: potential sensitizers for the two-photon photodynamic therapy of tumors , 2004, Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology.

[41]  N. Armaroli,et al.  Highly Luminescent CuI Complexes for Light‐Emitting Electrochemical Cells , 2006 .

[42]  E. Collet,et al.  First single-crystal synthesis and low-temperature structural determination of the quasi-2D quantum spin compound (CuCl)LaNb2O7. , 2011, Dalton transactions.

[43]  Philip Coppens,et al.  On the Biexponential Decay of the Photoluminescence of the Two Crystallographically-Independent Molecules in Crystals of [Cu(I)(phen)(PPh3)2][BF4]. , 2013, The journal of physical chemistry letters.

[44]  Harold C. Urey,et al.  Abundances of the elements , 1956 .

[45]  G. Meyer,et al.  MLCT excited states of cuprous bis-phenanthroline coordination compounds , 2000 .

[46]  D. McMillin,et al.  Photoluminescence from copper(I) complexes with low-lying metal-to-ligand charge transfer excited states , 1978 .

[47]  Catherine E Housecroft,et al.  Copper(I) dye-sensitized solar cells with [Co(bpy)3](2+/3+) electrolyte. , 2013, Chemical communications.

[48]  J. Burstyn,et al.  Photophysical characteristics and reactivity of bis(2,9-di-tert-butyl-1,10-phenanthroline)copper(I). , 2009, Inorganic chemistry.

[49]  A. Soldatov,et al.  Quantitative local structure refinement from XANES: multi-dimensional interpolation approach. , 2006, Journal of synchrotron radiation.

[50]  I. Tavernelli,et al.  Solvent-induced luminescence quenching: static and time-resolved X-ray absorption spectroscopy of a copper(I) phenanthroline complex. , 2013, The journal of physical chemistry. A.

[51]  Koichi Nozaki,et al.  Structure-dependent photophysical properties of singlet and triplet metal-to-ligand charge transfer states in copper(I) bis(diimine) compounds. , 2003, Inorganic chemistry.

[52]  M. W. George,et al.  Energy Dispersive XAFS: Characterization of Electronically Excited States of Copper(I) Complexes , 2013, The journal of physical chemistry. B.

[53]  T. Tahara,et al.  Real-time observation of the photoinduced structural change of bis(2,9-dimethyl-1,10-phenanthroline)copper(I) by femtosecond fluorescence spectroscopy: a realistic potential curve of the Jahn-Teller distortion. , 2007, Journal of the American Chemical Society.

[54]  M. Sliwa,et al.  New heteroleptic bis-phenanthroline copper(I) complexes with dipyridophenazine or imidazole fused phenanthroline ligands: spectral, electrochemical, and quantum chemical studies. , 2011, Inorganic chemistry.

[55]  M. Schmittel,et al.  Self-assembly of heteroleptic [2 x 2] and [2 x 3] nanogrids. , 2004, Chemical communications.

[56]  D. McMillin,et al.  Two-photon photochemistry of bis(2,9-dimethyl-1,10-phenanthroline)copper(1+) , 1987 .

[57]  J. Zink,et al.  Influence of ligand substitution on excited state structural dynamics in Cu(I) bisphenanthroline complexes. , 2010, The journal of physical chemistry. B.

[58]  D. McMillin,et al.  Structural and photophysical studies of Cu(NN)2+ systems in the solid state. Emission at last from complexes with simple 1,10-phenanthroline ligands. , 2000, Inorganic chemistry.

[59]  D. McMillin,et al.  Flash photolysis and quenching studies of copper(I) systems in the presence of Lewis bases: inorganic exciplexes? , 1987 .

[60]  Vincenzo Balzani,et al.  Electrochemically and Photochemically Driven Ring Motions in a Disymmetrical Copper [2]-Catenate. , 1997, Journal of the American Chemical Society.

[61]  Nosheen A. Gothard,et al.  Strong steric hindrance effect on excited state structural dynamics of Cu(I) diimine complexes. , 2012, The journal of physical chemistry. A.

[62]  G. B. Shaw,et al.  Ultrafast structural rearrangements in the MLCT excited state for copper(I) bis-phenanthrolines in solution. , 2006, Journal of the American Chemical Society.

[63]  C. Dietrich-Buchecker,et al.  Structure of a Synthetic Trefoil Knot Coordinated to Two Copper(I) Centers , 1990 .

[64]  Guy Jennings,et al.  MLCT state structure and dynamics of a copper(I) diimine complex characterized by pump-probe X-ray and laser spectroscopies and DFT calculations. , 2003, Journal of the American Chemical Society.

[65]  P. Gantzel,et al.  Structures of the Copper(I) and Copper(II) Complexes of 2,9-Diphenyl-1,10-phenanthroline: Implications for Excited-State Structural Distortion. , 1998, Inorganic chemistry.

[66]  T. Tahara,et al.  Substituent effect on the photoinduced structural change of Cu(I) complexes observed by femtosecond emission spectroscopy. , 2014, Physical chemistry chemical physics : PCCP.

[67]  Tahei Tahara,et al.  Coherent nuclear dynamics in ultrafast photoinduced structural change of bis(diimine)copper(I) complex. , 2011, Journal of the American Chemical Society.

[68]  D. McMillin,et al.  Exciplex quenching of photo-excitd copper complexes , 1985 .

[69]  D. McMillin,et al.  Simple Cu(I) complexes with unprecedented excited-state lifetimes. , 2002, Journal of the American Chemical Society.

[70]  M. Zgierski.  Cu(I)-2,9-dimethyl-1,10-phenanthroline: Density functional study of the structure, vibrational force-field, and excited electronic states , 2003 .

[71]  P. Gantzel,et al.  A Photoluminescent Copper(I) Complex with an Exceptionally High CuII /CuI Redox Potential: [Cu(bfp)2 ]+ (bfp=2,9-bis(trifluoromethyl)-1,10-phenanthroline). , 1998, Angewandte Chemie.

[72]  D. McMillin,et al.  Charge-transfer absorption and emission of Cu(NN)2+ systems , 1987 .

[73]  Vincenzo Balzani,et al.  Photochemistry and photophysics of coordination compounds , 2007 .

[74]  M. Neuburger,et al.  Copper(I) complexes of 6,6'-disubstituted 2,2'-bipyridine dicarboxylic acids: new complexes for incorporation into copper-based dye sensitized solar cells (DSCs). , 2009, Dalton transactions.

[75]  Roland E. Gamache,et al.  Temperature dependence of luminescence from Cu(NN)2+ systems in fluid solution. Evidence for the participation of two excited states , 1983 .

[76]  X. Lu,et al.  Can Polypyridyl Cu(I)-based Complexes Provide Promising Sensitizers for Dye-Sensitized Solar Cells? A Theoretical Insight into Cu(I) versus Ru(II) Sensitizers , 2011 .

[77]  C. Housecroft,et al.  Improving the photoresponse of copper(I) dyes in dye-sensitized solar cells by tuning ancillary and anchoring ligand modules. , 2013, Dalton transactions.

[78]  A. Soldatov,et al.  Three-dimensional local structure of photoexcited Cu diimine complex refined by quantitative XANES analysis. , 2008, The journal of physical chemistry. A.

[79]  Edward A. Stern,et al.  New Technique for Investigating Noncrystalline Structures: Fourier Analysis of the Extended X-Ray—Absorption Fine Structure , 1971 .

[80]  W. R. Robinson,et al.  Steric effects and the behavior of Cu(NN)(PPh3)2+ systems in fluid solution. Crystal and molecular structures of [Cu(dmp)(PPh3)2]NO3 and [Cu(phen)(PPh3)2]NO3.1.5EtOH , 1985 .

[81]  M. Ratner,et al.  Effects of electronic and nuclear interactions on the excited-state properties and structural dynamics of copper(I) diimine complexes. , 2013, The journal of physical chemistry. B.

[82]  Gianluca Accorsi,et al.  Electrophosphorescent homo- and heteroleptic copper(I) complexes prepared from various bis-phosphine ligands. , 2007, Chemical communications.

[83]  S. Sakaki,et al.  Synthesis of a new copper(I) complex, [Cu(tmdcbpy)2]+ (tmdcbpy = 4,4′,6,6′-tetramethyl-2,2′-bipyridine-5,5′-dicarboxylic acid), and its application to solar cells , 2002 .

[84]  K. Hodgson,et al.  X-ray absorption edge determination of the oxidation state and coordination number of copper: application to the type 3 site in Rhus vernicifera laccase and its reaction with oxygen , 1987 .

[85]  K. Henrick,et al.  Crystal and molecular structures of bis(4,4',6,6'-tetramethyl-2,2'-bipyridyl)copper(I) perchlorate, bis(4,4',6,6'-tetramethyl-2,2'-bipyridyl)copper(II) diperchlorate, and bis(4,4',6,6'-tetramethyl-2,2'-bipyridyl)copper(II) diperchlorate dihydrate. A search for copper(II) and copper(I) complexes with , 1982 .

[86]  Christian Bressler,et al.  Molecular structural dynamics probed by ultrafast X-ray absorption spectroscopy. , 2010, Annual review of physical chemistry (Print).

[87]  D. Rorabacher,et al.  Electron transfer by copper centers. , 2004, Chemical reviews.

[88]  J. Gisselbrecht,et al.  Copper(I) complexes of 1,10-phenanthroline–oligophenylenevinylene conjugates , 2003 .

[89]  J. Burstyn,et al.  Facile oxidation-based synthesis of sterically encumbered four-coordinate bis(2,9-di-tert-butyl-1,10-phenanthroline)copper(I) and related three-coordinate copper(I) complexes. , 2007, Inorganic chemistry.