Catalyzing Singlet Fission by Transition Metals:Second versus Third Row Effects  

作　　者：Yuxuan Hou Ilias Papadopoulos Yifan Bo Anna-Sophie Wollny Michael J.Ferguson Lukas A.Mai Rik R.Tykwinski Dirk M.Guldi 

机构地区：[1]Department of Chemistry,University of Alberta,Edmonton,Alberta T6G 2G2,Canada [2]Department of Chemistry and Pharmacy&Interdisciplinary Center for Molecular Materials(ICMM),Friedrich-Alexander-University Erlangen-Nuremberg,91058 Erlangen,Germany [3]Department of Applied Chemistry,Graduate School of Engineering,Center for Molecular Systems(CMS),Kyushu University,744 Moto-oka,Nishi-ku,Fukuoka 819-0395,Japan

出　　处：《Precision Chemistry》2023年第9期555-564,共10页精准化学（英文）

摘　　要：The synthesis and characterization of platinum(II)and palladium(II)complexes bearing two(dimers Pt(L_(pc))_(2)Cl_(2)and Pd(L_(pc))_(2)Cl_(2)),one(monomers Pt(L_(pc))(L_(ref))Cl_(2)and Pd(L_(pc))(L_(ref))-Cl_(2)),or no(reference compounds Pt(L_(ref))_(2)Cl_(2)and Pd(L_(ref))_(2)Cl_(2))pentacene-based pyridyl ligands are presented.Photophysical properties of the dimers are probed by means of steady-state and time-resolved transient absorption measurements in compar-ison to the monomer and model compounds.Our results document that despite enhanced spin−orbit coupling from the presence of heavy atoms,intramolecular singlet fission(iSF)is not challenged by intersystem crossing.iSF thus yields correlated triplet pairs and even uncorrelated triplet excited states upon decoherence.Importantly,significant separation of the two pentacenyl groups facilitates decoupling of the two chromophores.Furthermore,the mechanism of iSF is altered depending on the respective metal center,that is,Pt(II)versus Pd(II).The dimer based on Pt(II),Pt(L_(pc))2Cl_(2),exhibits a direct pathway for the iSF and forms a correlated triplet pair with singlet−quintet spin-mixing within 10 ns in variable solvents.On the other hand,the dimer based on Pd(II),Pd(L_(pc))_(2)Cl_(2),leads to charge transfer mixing during the population of the correlated triplet pair that is dependent on solvent polarity.Moreover,Pd(L_(pc))_(2)Cl_(2)gives rise to a stable equilibrium between singlet and quintet correlated triplet pairs with lifetimes of up to 170 ns.Inherent differences in the size and polarizability,when contrasting platinum(II)with palladium(II),are the most likely rationale for the underlying trends.

关 键 词：metal complexes singlet fission pentacene dimers ultrafast spectroscopy electronic coupling 

分 类 号：O62[理学—有机化学]