Matthew T Whited

Publications of Matthew T Whited

• Cu4I4 clusters supported by P^N-type ligands: new structures with tunable emission colors.

  Authors: Zhiwei Liu, Peter I Djurovich, Matthew T Whited, Mark E Thompson

  Inorganic chemistry. 12/2011; 51(1):230-6.

  A series of Cu(4)I(4) clusters (1-5) supported by two P^N-type ligands 2-[(diRphosphino)methyl]pyridine (1, R = phenyl; 2, R = cyclohexyl; 3, R = tert-butyl; 4, R = iso-propyl; 5, R = ethyl) haveA series of Cu(4)I(4) clusters (1-5) supported by two P^N-type ligands 2-[(diRphosphino)methyl]pyridine (1, R = phenyl; 2, R = cyclohexyl; 3, R = tert-butyl; 4, R = iso-propyl; 5, R = ethyl) have been synthesized. Single crystal X-ray analyses show that all five clusters adopt a rare "octahedral" geometry. The central core of the cluster consists of the copper atoms arranged in a parallelogram with μ(4)-iodides above and below the copper plane. The copper atoms on the two short edges of the parallelogram (Cu-Cu = 2.525(2)-2.630(1) Å) are bridged with μ(2)-iodides, whereas the long edges (Cu-Cu = 2.839(3)-3.035(2) Å) are bridged in an antiparallel fashion by the P^N ligands. This Cu(4)I(4) geometry differs significantly from the "cubane" and "stairstep" geometries reported for other Cu(4)I(4)L(4) clusters. Luminescence spectra of clusters 3 and 4 display a single emission around 460 nm at room temperature that is assigned to emission from a triplet halide-to-ligand charge-transfer ((3)XLCT) excited state, whereas clusters 1, 2, and 5 also have a second band around 570 nm that is assigned to a Cu(4)I(4) cluster-centered ((3)CC) excited state. The structural and photophysical properties of a dinuclear Cu(2)I(2)(P^N)(2) complex obtained during the sublimation of cluster 3 is also provided.

• Symmetry-breaking intramolecular charge transfer in the excited state of meso-linked BODIPY dyads.

  Authors: Matthew T Whited, Niral M Patel, Sean T Roberts, Kathryn Allen, Peter I Djurovich, Stephen E Bradforth, Mark E Thompson

  Chemical communications (Cambridge, England). 11/2011; 48(2):284-6.

  We report the synthesis and characterization of symmetric BODIPY dyads where the chromophores are attached at the meso position, using either a phenylene bridge or direct linkage. Both moleculesWe report the synthesis and characterization of symmetric BODIPY dyads where the chromophores are attached at the meso position, using either a phenylene bridge or direct linkage. Both molecules undergo symmetry-breaking intramolecular charge transfer in the excited state, and the directly linked dyad serves as a visible-light-absorbing analogue of 9,9'-bianthryl.

• A codeposition route to CuI-pyridine coordination complexes for organic light-emitting diodes.

  Authors: Zhiwei Liu, Munzarin F Qayyum, Chao Wu, Matthew T Whited, Peter I Djurovich, Keith O Hodgson, Britt Hedman, Edward I Solomon, Mark E Thompson

  Journal of the American Chemical Society. 03/2011; 133(11):3700-3.

  We demonstrate a new approach for utilizing CuI coordination complexes as emissive layers in organic light-emitting diodes that involves in situ codeposition of CuI and 3,5-bis(carbazol-9-yl)pyridineWe demonstrate a new approach for utilizing CuI coordination complexes as emissive layers in organic light-emitting diodes that involves in situ codeposition of CuI and 3,5-bis(carbazol-9-yl)pyridine (mCPy). With a simple three-layer device structure, pure green electroluminescence at 530 nm from a Cu(I) complex was observed. A maximum luminance and external quantum efficiency (EQE) of 9700 cd/m(2) and 4.4%, respectively, were achieved. The luminescent species was identified as [CuI(mCPy)(2)](2) on the basis of photophysical studies of model complexes and X-ray absorption spectroscopy.

• Substituted 1,3-bis(imino)isoindole diols: a new class of proton transfer dyes.

  Authors: Kenneth Hanson, Niral Patel, Matthew T Whited, Peter I Djurovich, Mark E Thompson

  Organic letters. 03/2011; 13(7):1598-601.

  A new class of excited-state intramolecular proton transfer (ESIPT) dyes based on a 1,3-bis(imino)isoindole diol motif has been prepared. These molecules exhibit orange emission (∼600 nm) with aA new class of excited-state intramolecular proton transfer (ESIPT) dyes based on a 1,3-bis(imino)isoindole diol motif has been prepared. These molecules exhibit orange emission (∼600 nm) with a large apparent Stokes shift (>6000 cm(-1)) and quantum efficiencies up to 45%. Selective modification of the substituents can be used to shift the equilibrium between the enol and keto forms of the molecule in both the ground and excited states.

• Singlet and triplet excitation management in a bichromophoric near-infrared-phosphorescent BODIPY-benzoporphyrin platinum complex.

  Authors: Matthew T Whited, Peter I Djurovich, Sean T Roberts, Alec C Durrell, Cody W Schlenker, Stephen E Bradforth, Mark E Thompson

  Journal of the American Chemical Society. 01/2011; 133(1):88-96.

  Multichromophoric arrays provide one strategy for assembling molecules with intense absorptions across the visible spectrum but are generally focused on systems that efficiently produce andMultichromophoric arrays provide one strategy for assembling molecules with intense absorptions across the visible spectrum but are generally focused on systems that efficiently produce and manipulate singlet excitations and therefore are burdened by the restrictions of (a) unidirectional energy transfer and (b) limited tunability of the lowest molecular excited state. In contrast, we present here a multichromophoric array based on four boron dipyrrins (BODIPY) bound to a platinum benzoporphyrin scaffold that exhibits intense panchromatic absorption and efficiently generates triplets. The spectral complementarity of the BODIPY and porphryin units allows the direct observation of fast bidirectional singlet and triplet energy transfer processes (k(ST)((1)BDP→(1)Por) = 7.8 × 10(11) s(-1), k(TT)((3)Por→(3)BDP) = 1.0 × 10(10) s(-1), k(TT)((3)BDP→(3)Por) = 1.6 × 10(10) s(-1)), leading to a long-lived equilibrated [(3)BDP][Por]⇌[BDP][(3)Por] state. This equilibrated state contains approximately isoenergetic porphyrin and BODIPY triplets and exhibits efficient near-infrared phosphorescence (λ(em) = 772 nm, Φ = 0.26). Taken together, these studies show that appropriately designed triplet-utilizing arrays may overcome fundamental limitations typically associated with core-shell chromophores by tunable redistribution of energy from the core back onto the antennae.

• Synthesis and characterization of phosphorescent three-coordinate Cu(I)-NHC complexes.

  Authors: Valentina A Krylova, Peter I Djurovich, Matthew T Whited, Mark E Thompson

  Chemical communications (Cambridge, England). 09/2010; 46(36):6696-8.

  Cationic and neutral monomeric three-coordinate phosphorescent Cu(I) complexes were synthesized and characterized by XRD analysis, electrochemistry and photophysical studies in differentCationic and neutral monomeric three-coordinate phosphorescent Cu(I) complexes were synthesized and characterized by XRD analysis, electrochemistry and photophysical studies in different environments. DFT calculations have aided the assignment of the electronic structure and excited state behavior of these complexes.

• Efficient dipyrrin-centered phosphorescence at room temperature from bis-cyclometalated iridium(III) dipyrrinato complexes.

  Authors: Kenneth Hanson, Arnold Tamayo, Vyacheslav V Diev, Matthew T Whited, Peter I Djurovich, Mark E Thompson

  Inorganic chemistry. 07/2010; 49(13):6077-84.

  A series of seven dipyrrin-based bis-cyclometalated Ir(III) complexes have been synthesized and characterized. All complexes display a single, irreversible oxidation wave and at least one reversibleA series of seven dipyrrin-based bis-cyclometalated Ir(III) complexes have been synthesized and characterized. All complexes display a single, irreversible oxidation wave and at least one reversible reduction wave. The electrochemical properties were found to be dominated by dipyrrin centered processes. The complexes were found to display room temperature luminescence with emission maxima ranging from 658 to 685 nm. Through systematic variation of the cyclometalating ligand and the meso substituent of the dipyrrin moiety, it was found that the observed room temperature emission was due to phosphorescence from a dipyrrin-centered triplet state with quantum efficiencies up to 11.5%. Bis-cyclometalated Ir(III) dipyrrin based organic light emitting diodes (OLEDs) display emission at 682 nm with maximum external quantum efficiencies up to 1.0%.

• Late Metal Carbene Complexes Generated by Multiple C-H Activations: Examining the Continuum of M horizontal lineC Bond Reactivity.

  Authors: Matthew T. Whited, Robert H. Grubbs

  Accounts of chemical research. 08/2009;

  Unactivated C(sp(3))-H bonds are ubiquitous in organic chemicals and hydrocarbon feedstocks. However, these resources remain largely untapped, and the development of efficient homogeneous methods forUnactivated C(sp(3))-H bonds are ubiquitous in organic chemicals and hydrocarbon feedstocks. However, these resources remain largely untapped, and the development of efficient homogeneous methods for hydrocarbon functionalization by C-H activation is an attractive and unresolved challenge for synthetic chemists. Transition-metal catalysis offers an attractive possible means for achieving selective, catalytic C-H functionalization given the thermodynamically favorable nature of many desirable partial oxidation schemes and the propensity of transition-metal complexes to cleave C-H bonds. Selective C-H activation, typically by a single cleavage event to produce M-C(sp(3)) products, is possible through myriad reported transition-metal species. In contrast, several recent reports have shown that late transition metals may react with certain substrates to perform multiple C-H activations, generating M horizontal lineC(sp(2)) complexes for further elaboration. In light of the rich reactivity of metal-bound carbenes, such a route could open a new manifold of reactivity for catalytic C-H functionalization, and we have targeted this strategy in our studies. In this Account, we highlight several early examples of late transition-metal complexes that have been shown to generate metal-bound carbenes by multiple C-H activations and briefly examine factors leading to the selective generation of metal carbenes through this route. Using these reports as a backdrop, we focus on the double C-H activation of ethers and amines at iridium complexes supported by Ozerov's amidophosphine PNP ligand (PNP = [N(2-P(i)Pr(2)-4-Me-C(6)H(3))(2)](-)), allowing isolation of unusual square-planar iridium(I) carbenes. These species exhibit reactivity that is distinct from the archetypal Fischer and Schrock designations. We present experimental and theoretical studies showing that, like the classical square-planar iridium(I) organometallics, these complexes are best described as nucleophilic at iridium. We discuss the classification of this reactivity in the context of a scheme originally delineated by Roper. These "Roper-type" carbenes perform a number of multiple-bond metatheses leading to atom and group transfer from electrophilic heterocumulene (e.g., CO(2), CS(2), PhNCS) and diazo (e.g., N(2)O, AdN(3)) reagents. In one instance, we have extended this methodology to a process for catalytic C-H functionalization by a double C-H activation-group transfer process. Although the scope of these reactions is currently limited, these new pathways may find broader utility as the reactivity of late-metal carbenes continues to be explored. Examination of alternative transition metals and supporting ligand sets will certainly be important. Nonetheless, our findings show that carbene generation by double C-H activation is a viable strategy for C-H functionalization, leading to products not accessible through traditional C(sp(3))-H activation pathways.

• Dinitrogen Complexes Supported by Tris(phosphino)silyl Ligands.

  Authors: Matthew T Whited, Neal P Mankad, Yunho Lee, Paul F Oblad, Jonas C Peters

  Inorganic chemistry. 03/2009;

  The tetradentate tris(phosphino)silyl ligand [SiP(iPr)(3)] ([SiP(iPr)(3)] = [Si(o-C(6)H(4)P(i)Pr(2))(3)](-)) has been prepared, and its complexation with iron, cobalt, nickel, and iridium precursorsThe tetradentate tris(phosphino)silyl ligand [SiP(iPr)(3)] ([SiP(iPr)(3)] = [Si(o-C(6)H(4)P(i)Pr(2))(3)](-)) has been prepared, and its complexation with iron, cobalt, nickel, and iridium precursors has been explored. Several coordination complexes have been thoroughly characterized and are described. These include, for example, the divalent trigonal bipyramidal metal chlorides [SiP(iPr)(3)]M-Cl (M = Fe, Co, Ni), as well as the monovalent dinitrogen adducts [SiP(iPr)(3)]M-N(2) (M = Fe, Co, Ir), which are compared with related [SiP(Ph)(3)]M-Cl and [SiP(Ph)(3)]M-N(2) species (M = Fe, Co). Complexes of this type represent the first examples of terminal dinitrogen adducts of monovalent iron, and the ligand architecture allows examination of a unique class of dinitrogen adducts with a trans-disposed silyl donor. Oxidation of the appropriate [SiP(R)(3)]M-N(2) precursors affords the divalent iron triflate [SiP(Ph)(3)]Fe(OTf) and trivalent cobalt triflate {[SiP(iPr)(3)]Co(OTf)}{OTf} complexes, which are of interest for group transfer studies because of the presence of a labile triflate ligand. Comparative electrochemical, structural, and spectroscopic data are provided for these complexes.

• A catalytic cycle for oxidation of tert-butyl methyl ether by a double C-H activation-group transfer process.

  Authors: Matthew T. Whited, Robert H. Grubbs

  Journal of the American Chemical Society. 01/2009; 130(49):16476-7.

• Oxygen-atom transfer from carbon dioxide to a Fischer carbene at (PNP)Ir.

  Authors: Matthew T. Whited, Robert H. Grubbs

  Journal of the American Chemical Society. 06/2008; 130(18):5874-5.

• Terminal FeI-N2 and FeII...H-C interactions supported by tris(phosphino)silyl ligands.

  Authors: Neal P Mankad, Matthew T Whited, Jonas C Peters

  Angewandte Chemie (International ed. in English). 02/2007; 46(30):5768-71.

• Complexes of iron and cobalt with new tripodal amido-polyphosphine hybrid ligands.

  Authors: Matthew T Whited, Eric Rivard, Jonas C Peters

  Chemical communications (Cambridge, England). 05/2006;

  Divalent complexes of iron and cobalt with new, monoanionic tripodal amido-polyphosphine ligands have been thoroughly characterized, and XRD analysis reveals geometries that are distinct for thisDivalent complexes of iron and cobalt with new, monoanionic tripodal amido-polyphosphine ligands have been thoroughly characterized, and XRD analysis reveals geometries that are distinct for this class of ligand.

• Factors Dictating Carbene Formation at (PNP)Ir

  Authors: Nigel J Brookes, Matthew T. Whited, Alireza Ariafard, Robert Stranger, Robert H. Grubbs, Brian F Yates

  The mechanistic subtleties involved with the interaction of an amido/bis(phosphine)-supported (PNP)Ir fragment with a series of linear and cyclic ethers have been investigated using densityThe mechanistic subtleties involved with the interaction of an amido/bis(phosphine)-supported (PNP)Ir fragment with a series of linear and cyclic ethers have been investigated using density functional theory. Our analysis has revealed the factors dictating reaction direction toward either an iridium-supported carbene or a vinyl ether adduct. The (PNP)Ir structure will allow carbene formation only from accessible carbons α to the ethereal oxygen, such that d electron back-donation from the metal to the carbene ligand is possible. Should these conditions be unavailable, the main competing pathway to form vinyl ether can occur, but only if the (PNP)Ir framework does not sterically interfere with the reacting ether. In situations where steric hindrance prevents unimpeded access to both pathways, the reaction may progress to the initial C−H activation but no further. Our mechanistic analysis is density functional independent and whenever possible confirmed experimentally by trapping intermediate species experimentally. We have also highlighted an interesting systematic error present in the DFT analysis of reactions where steric environment alters considerably within a reaction.

• Elucidation of heterocumulene activation by a nucleophilic-at-metal iridium(I) carbene

  Authors: Matthew T. Whited, Robert H. Grubbs

  A carbene complex supported by the (PNP)Ir framework is shown to facilitate sulfur-atom transfer from CS2 and PhNCS by an unusual multiple-bond metathesis pathway, and kinetically trappedA carbene complex supported by the (PNP)Ir framework is shown to facilitate sulfur-atom transfer from CS2 and PhNCS by an unusual multiple-bond metathesis pathway, and kinetically trapped intermediates are provided to support the proposed metal-initiated mechanism for heterocumulene activation. Experimental and theoretical studies on a series of (PNP)Ir-L complexes suggest that a high-lying, nucleophilic Ir(dg) orbital mediates this unique reactivity. The combination of evidence indicates that square-planar Ir(I) carbenes of this type are best formulated as nucleophilic-at-metal carbenes, exhibiting reactivity initiated by a nucleophilic metal center rather than a nucleophilic or electrophilic carbene and providing products that are complementary to those typically observed for high-valent alkylidenes.

• Probing the C-H Activation of Linear and Cyclic Ethers at (PNP)Ir

  Authors: Matthew T. Whited, Yanjun Zhu, Samuel D. Timpa, Chun-Hsing Chen, Bruce M Foxman, Oleg V Ozerov, Robert H. Grubbs

  Interaction of the amido/bis(phosphine)-supported (PNP)Ir fragment with a series of linear and cyclic ethers is shown to afford, depending on substrate, products of α,α-dehydrogenation (carbenes),Interaction of the amido/bis(phosphine)-supported (PNP)Ir fragment with a series of linear and cyclic ethers is shown to afford, depending on substrate, products of α,α-dehydrogenation (carbenes), α,β-dehydrogenation (vinyl ethers), or decarbonylation. While carbenes are exclusively obtained from tert-amyl methyl ether, sec-butyl methyl ether (SBME), n-butyl methyl ether (NBME), and tetrahydrofuran (THF), vinyl ethers or their adducts are observed upon reaction with diethyl ether and 1,4-dioxane. Decarbonylation occurs upon interaction of (PNP)Ir with benzyl methyl ether, and a mechanism is proposed for this unusual transformation, which occurs via a series of C−H, C−O, and C−C bond cleavage events. The intermediates characterized for several of these reactions as well as the α,α-dehydrogenation of tert-butyl methyl ether (MTBE) are used to outline a reaction pathway for the generation of PNP-supported iridium(I) carbene complexes, and it is shown that the long-lived, observable intermediates are substrate-dependent and differ for the related cases of MTBE and THF. Taken together, these findings highlight the variety of pathways utilized by the electron-rich, unsaturated (PNP)Ir fragment to stabilize itself by transferring electron density to ethereal substrates through oxidative addition and/or the formation of π-acidic ligands.