Mechanical vs Electronic Strain: Calculated Configurations of Alkynyl-Pt(II)-Phosphine Macrocycles

Abstract

Optimized geometries of macrocycles composed of four Pt(PR 3 ) 2 linkers and four rods terminated with ethynyl or pyridyl moieties have been calculated at the PBE0/Def2-TZVPP//PBE0/Def2-SVP level of density functional theory for all combinations of cis and trans configurations at the Pt centers. For uncharged complexes with four p,p′-bis(ethynyl)biphenyl rods and neutral Pt centers, the energy of the planar oval-shaped all-trans isomer lies 17 kcal/mol below that of the puckered square-shaped all-cis isomer. In this case, the electronic strain associated with the cis arrangement at the Pt atoms overrules the mechanical strain associated with the bending of triple bonds. For cationic complexes containing two bipyridyl and two p,p′bis(ethynyl)biphenyl rods, with a +1 charge on each Pt center, a puckered rectangular structure with all-cis Pt centers is found to be 38 kcal/mol lower in energy than the isomer with all four Pt centers trans. The results have been analyzed in terms of three additive factors, referred to as electronic, mechanical, and electrostatic strains.

Macrocyclic Complexes Derived from Four cis‐L2Pt Corners and Four Butadiynediyl Linkers; Syntheses, Electronic Structures, and Square versus Skew Rhombus Geometries

“…Contrasting puckered vs. planar geometries have also been found for two related macrocyclic tetraplatinum alkynyl species, one of which was accessed via self‐assembly [30] . For each adduct, the equilibrium has been studied by DFT, and analyzed in terms of electronic, mechanical, and electronic strain [30b] …”

Synthesis of a platinacycle: determination of the structure and examination of the photophysical properties based on DFT calculations

“…23 Platinacycles bearing the Pt-bipyridine bis(acetylide) complex and binaphthol moieties emit light in the near-infrared region upon doping into poly(Nvinylcarbazole) film. 24 Although platinacycles fascinate researchers in the fields of supramolecular chemistry and photo-electrically functional materials as well as organometallic chemistry, [25][26][27][28][29][30][31] there have been fewer reports on the synthesis of platinacycles bearing Pt-2,2′-bipyridine bis(acetylide) complex moieties. This is presumably due to the poor solubility introduced by this kind of skeleton, resulting in difficult synthesis.…”