3rd Edition of

Chemistry World Conference

June 14-15, 2023 | Online Event

Chemistry 2023

Obadah Subhi Abdel Rahman

Speaker at Chemistry World Conference 2023 - Obadah Subhi Abdel Rahman
King Faisal University (KFU), Saudi Arabia
Title : Synthesis, investigation, and DFT studies on Bis(alkenylruthenium) complexes with free? Rotating and rotationally restricted biaryl bridges


A new series of biaryl-bridged dinuclear alkenylruthenium complexes with varied torsion angle ? between the planes of the phenyl rings have been prepared via regio- and stereospecific insertion of the -C≡CH bond of the corresponding terminal 4,4’-diethynylbiphenyl derivatives into the Ru-H bond of the hydride complex HRu(CO)Cl(PiPr3)2 (Figure 1)[1]. These square pyramidal five-coordinated, 16-valence electrons (VEs) complexes have been characterized in their neutral state by usual IR, UV/Vis and NMR spectroscopy, and in their two different accessible oxidized states, by IR, UV/Vis/NIR spectroelectrochemistry and by EPR spectroscopy as well as by electrochemical methods and by (TD)-DFT calculations. Our results indicate that the torsion angle strongly modulates and tunes the electronic coupling between the two ruthenium-vinyl moieties significantly. They confirm that σ-bonded divinylbiphenylenes constitute a particularly interesting class of non-innocent ligands in organometallic systems. Electrochemical studies showed that these complexes undergo two reversible, consecutive one-electron oxidation processes. The splitting of the redox waves, ΔE½, and the comproportionation constants (Kc) vary as the torsion angle changes, suggesting a strong electronic interaction between the two styryl ruthenium moieties (Kc = 2.9×103) when the two phenyl rings are planar, and a weak interaction (Kc = 18) when they are orthogonal to each other. In IR spectroelectrochemistry, the magnitude of the CO band shifts and the band splitting in the mixed-valent radical cations likewise depend significantly on the torsion angle between the planes of the two phenyl rings. Charge distributions in the radical cations vary from 67:33% when biphenyl bridge is close to planar to 97:3% when the phenyl rings are orthogonal to each other. Complexes with low torsion angle display strong electrochromic behaviour in three distinct states with a strong NIR band in their mixed-valent states. No such band was, however, observed in the case where the two phenyl rings are orthogonal to each other.

Audience Take Away: 

  • Spectroelectrochemistry.
  • Non-innocent ligands in organometallic systems. 
  • Bis(alkenylruthenium) organometallic chemistry.
  • (TD)-DFT calculations.
  • Torsion angle


Obadah Subhi Abdel-Rahman received his B.Sc. M.Sc. degrees in 2007 and 2009, respectively, from the Hashemite University (Jordan) and his Ph.D. degree with the honour degree (magna cum laude) in 2015 from Konstanz University (Germany) in inorganic chemistry. He was working as an inorganic lecturer at Tabuk University (Saudi Arabia Sep. 2010 - Aug. 2011), teaching assistant at The Hashemite University (Jordan, Oct. 2007 - Oct. 2009), and as an assistance professor of inorganic chemistry at Jerash University (Jordan Sep. 2016 – Sep. 2019). Currently, he is working since Sep. 2019 as an assistance professor of inorganic chemistry at King Faisal University (Saudi Arabia). His research activities include: (i) Multinuclear and organometallic compounds with redox-active, alkenyl non-innocent ligands. (ii) Redox-active π-conjugated metal-organic molecules where the organic bridge molecules constitute an integral part of a delocalized π-system. (iv) Electrochromic materials and redox-responsive dyes. (v) Organometallic molecule-based conductive material and molecular wires