6943-11-9Relevant academic research and scientific papers
Effect of Structure on the Spin-Spin Interactions of Tethered Dicyanomethyl Diradicals
Zhang, Rui,Peterson, Joshua P.,Fischer, Logan J.,Ellern, Arkady,Winter, Arthur H.
supporting information, p. 14308 - 14313 (2018/10/24)
Stable organic radicals with switchable spin states have attracted attention for a variety of applications, but a fundamental understanding of how radical structure effects the weak bonding interactions between organic radicals is limited. To evaluate the effect of chemical structure on the strength and nature of such spin interactions, a series of 14 tethered aryl dicyanomethyl diradicals were synthesized, and the structure and thermodynamic properties of the diradicals were investigated. These studies indicate that the nature of the dimer and the equilibrium thermodynamic parameters of the diradical-dimer equilibria are highly sensitive to the attachment point of the linker, the length of the linker, and the substituents on the radical itself. Values of the intramolecular Ka vary from as small as 5 to as high as 105 depending on these variables. An X-ray crystal structure for a linked ortho-substituted diradical shows that the diradical forms an intramolecular sigma dimer in the crystalline state with an elongated C-C bond (1.637 ?). Subtle changes to the radical structure influences the nature of the spin interactions, as fixing the dimethylamino substituent on the radical into a ring to make a julolidine-derived diradical leads to the weakest bonding interaction observed (ΔGbonding = 1 kcal mol-1) and changes the spin-paired species from a sigma dimer to a diradical pimer. This work has implications for the design of stimuli-responsive materials that can reversibly switch between the dramatically different properties of closed-shell species and the unique properties of diradicals.
Dibenzo[a,e]pentalenophanes: Bending a Non-Alternant Hydrocarbon
Hermann, Mathias,Wassy, Daniel,Kratzert, Daniel,Esser, Birgit
supporting information, p. 7374 - 7387 (2018/05/04)
In cyclophanes, an aromatic moiety is incorporated into a (strained) cyclic structure. Of particular interest as model systems for bent carbon nanostructures are those containing polycyclic aromatic hydrocarbons. Dibenzo[a,e]pentalene (DBP) is a non-alternant polycyclic hydrocarbon with small band gap and tunable optoelectronic properties. However, changing these properties by bending of the DBP structure has yet to be investigated. Herein, we report the synthesis, optoelectronic, and structural properties of (2,7)dibenzo[a,e]pentalenophanes with four different bridge sizes and bending angles of the DBP unit, accompanied by (TD)DFT calculations. The last, strain-inducing dehydration reaction was accomplished by using Burgess’ reagent. The HOMO and LUMO levels and the magnetic shielding of protons pointing inside the cyclophane cavity grew stepwise with increasing ring strain. Single-crystal X-ray structures of the smallest three derivatives revealed a near semi-circle and a bend angle of the DBP unit of almost 88° for the smallest derivative. We demonstrated the synthetic versatility of our approach by varying the substituents at the DBP unit, allowing for further tuning of optoelectronic properties. The synthetic strategy presented herein may pave the way for the synthesis of conjugated DBP nanorings.
Synthesis of components for supramolecules incorporating cycloheptatriene building blocks
Neigenfink, J.,Martin, A.,Wendel, V.,Abraham, W.
experimental part, p. 632 - 641 (2011/10/13)
Molecular threads I-III incorporating 1,3,5-cycloheptatriene units have been synthesized by three methods. Bridges were designed as ether (9, 14, 18 and 22), ester (4 and 14) and amino functions (25), respectively. The attachment of a second aryl residue
Synthesis of Acetylene-Terminated α,ω-Bisphenoxyalkanes
Babirad, Stephan A.,Feld, William A.
, p. 140 - 141 (2007/10/02)
Nine, α,ω-bis(4-ethynylphenoxy)alkanes were synthesized from the corresponding α,ω-dibromoalkanes by (1) reaction with p-bromophenol/KOH, (2) palladium-catalyzed coupling with 2-methyl-3-butyn-2-ol, and (3) caustic hydrolysis of the hydroxy intermediates.The structures of the ethynyl compounds were confirmed by IR, (1)H NMR, and DSC.
