Michael Ghidiu
Drexel University
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Publication
Featured researches published by Michael Ghidiu.
Journal of the American Chemical Society | 2013
Allen J. Pistner; Daniel A. Lutterman; Michael Ghidiu; Ying-Zhong Ma; Joel Rosenthal
A homologous set of 5,5-dimethylphlorin macrocycles in which the identity of one aryl ring is systematically varied has been prepared. These derivatives contain ancillary pentafluorophenyl (3H(Phl(F))), mesityl (3H(Phl(Mes))), 2,6-bismethoxyphenyl (3H(Phl(OMe))), 4-nitrophenyl (3H(Phl(NO2))), or 4-tert-butylcarboxyphenyl (3H(Phl(CO2tBu))) groups at the 15-meso-position. These porphyrinoids were prepared in good yields (35-50%) and display unusual multielectron redox and photochemical properties. Each phlorin can be oxidized up to three times at modest potentials and can be reduced twice. The electron-donating and electron-releasing properties of the ancillary aryl substituent attenuate the potentials of these redox events; phlorins containing electron-donating aryl groups are easier to oxidize and harder to reduce, while the opposite trend is observed for phlorins containing electron-withdrawing functionalities. Phlorin substitution also has a pronounced effect on the observed photophysics, as introduction of electron-releasing aryl groups on the periphery of the macrocycle is manifest in larger emission quantum yields and longer fluorescence lifetimes. Each phlorin displays an intriguing supramolecular chemistry and can bind 2 equiv of fluoride. This binding is allosteric in nature, and the strength of halide binding correlates with the ability of the phlorin to stabilize the buildup of charge. Moreover, fluoride binding to generate complexes of the form 3H(Phl(R))·2F(-) modulates the redox potentials of the parent phlorin. As such, titration of phlorin with a source of fluoride represents a facile method to tune the ability of this class of porphyrinoid to absorb light and engage in redox chemistry.
Journal of Physical Chemistry C | 2014
Allen J. Pistner; Daniel A. Lutterman; Michael Ghidiu; Eric Walker; Glenn P. A. Yap; Joel Rosenthal
A new 5,5-dimethylphlorin derivative (3H(PhlCF3)) was prepared and studied through a combination of redox, photophysical, and computational experiments. The phlorin macrocycle is significantly distorted from planarity compared to more traditional tetrapyrrole architectures and displays solvatochroism in the soret region of the UV–vis spectrum (∼370–420 nm). DFT calculations indicate that this solvatochromic behavior stems from the polarized nature of the frontier orbital (LUMO+1) that is most heavily involved in these transitions. Compound 3H(PhlCF3) also displays an intriguing supramolecular chemistry with certain anions; this phlorin can cooperatively hydrogen-bond two equivalents of fluoride to form 3H(PhlCF3)·2F– but does not bind larger halides such as Cl– or Br–. Analogous studies revealed that the phlorin can hydrogen-bond with carboxylate anions such as acetate to form 1:1 complexes such as 3H(PhlCF3)·OAc–. These supramolecular assemblies are robust and form even in relatively polar solvents such as MeCN. Hydrogen-bonding of fluoride and acetate anions to the phlorin N–H residues significantly attenuates the redox and photophysical properties of the phlorin. Moreover, The ability to independently vary the size and pKa of a series of carboxylate hydrogen-bond acceptors has allowed us to probe how phlorin–anion association is controlled by the anion’s size and/or basicity. These studies elucidate the physical properties and the electronic effects that shape the supramolecular chemistry displayed by the phlorin platform.
Science Advances | 2018
Michael Ghidiu; Sankalp Kota; Vadym Drozd; Michel W. Barsoum
The interlayer spacing of the material Ti3C2 MXene expands under pressure due to intercalation of water. Pseudo-negative compressibility in layered materials is a phenomenon typically limited to in situ high-pressure experiments in some clay minerals and carbon-based materials. We show that the MXene Ti3C2Tx expands along its crystallographic c direction when compressed in the presence of H2O. This expansive effect occurs when a mixture of powders and excess water is quasi-hydrostatically compressed in a diamond anvil cell; it also occurs to a much larger extent when powders are pressed uniaxially into discs and, notably, persists after pressure is released. We attribute the expansion to the insertion of H2O molecules and have identified shear-induced slipping of the nanosheets comprising multilayered MXene particles as a possible cause of this behavior in the latter case. This both has implications for the processing of MXenes and contributes to the field of materials with pseudo-negative compressibility by adding a new member for further investigation.
Nature | 2014
Michael Ghidiu; Maria R. Lukatskaya; Meng-Qiang Zhao; Yury Gogotsi; Michel W. Barsoum
Chemical Communications | 2014
Michael Ghidiu; Michael Naguib; Chenyang Shi; Olha Mashtalir; L. M. Pan; B. Zhang; Jian Yang; Yury Gogotsi; Simon J. L. Billinge; Michel W. Barsoum
Physical Chemistry Chemical Physics | 2016
Michael Hope; Alexander C. Forse; Kent Griffith; Maria R. Lukatskaya; Michael Ghidiu; Yury Gogotsi; Clare P. Grey
Advanced Functional Materials | 2016
Andrew D. Dillon; Michael Ghidiu; Alex L. Krick; Justin Griggs; Steven J. May; Yury Gogotsi; Michel W. Barsoum; Aaron T. Fafarman
Chemistry of Materials | 2016
Michael Ghidiu; Joseph Halim; Sankalp Kota; David L. Bish; Yury Gogotsi; Michel W. Barsoum
Advanced Functional Materials | 2016
Chuanfang John Zhang; Seon Joon Kim; Michael Ghidiu; Meng-Qiang Zhao; Michel W. Barsoum; Valeria Nicolosi; Yury Gogotsi
Nano Energy | 2016
Meng-Qiang Zhao; Michelle Torelli; Chang E. Ren; Michael Ghidiu; Zheng Ling; Babak Anasori; Michel W. Barsoum; Yury Gogotsi