A New Electrically Conducting Metal–Organic Framework Featuring U-Shaped cis-Dipyridyl Tetrathiafulvalene Ligands

A new electrically conducting 3D metal-organic framework (MOF) with a unique architecture was synthesized using 1,2,4,5-tetrakis-(4-carboxyphenyl)benzene (TCPB) a redox-active cis-dipyridyl-tetrathiafulvalene (Z-DPTTF) ligand. While TCPB formed Zn2(COO)4 secondary building units (SBUs), instead of connecting the Zn2-paddlewheel SBUs located in different planes and forming a traditional pillared paddlewheel MOF, the U-shaped Z-DPTTF ligands bridged the neighboring SBUs formed by the same TCPB ligand like a sine-curve along the b axis that created a new sine-MOF architecture. The pristine sine-MOF displayed an intrinsic electrical conductivity of 1 × 10−8 S/m, which surged to 5 × 10−7 S/m after I2 doping due to partial oxidation of electron rich Z-DPTTF ligands that raised the charge-carrier concentration inside the framework. However, the conductivities of the pristine and I2-treated sine-MOFs were modest possibly because of large spatial distances between the ligands that prevented π-donor/acceptor charge-transfer interactions needed for effective through-space charge movement in 3D MOFs that lack through coordination-bond charge transport pathways.

Fast Reverse Intersystem Crossing Over 107 s-1 in Organic Emitters with Inverted Singlet-Triplet Gap via Intramolecular Through Space Charge Transfer

Controlling excited state properties to achieve fast reverse intersystem crossing rates of over 107 s-1 is still challenging for intramolecular through-space charge transfer (TSCT) based delayed fluorescent materials. To gain further insight into the relationship between through-space and through-bond charge transfer (TSCT/TBCT), herein, three compounds DPS-24Ac, DPS-25Ac and DPS-OAc were prepared and characterized via NMR, MS and single crystal, in which the diphenylsulfone (DPS) is used as the acceptor group and acridine (Ac) as the donor moiety. Intense emissions from blue to yellow with high emission efficiency of 70-100% are detected for all emitters. Both computations and experiments suggest that compounds DPS-24Ac and DPS-25Ac have a clear TSCT effect and also an inverted adiabatic singlet-triplet gap which can be explained by the kinetic exchange mechanism. Notably, compound DPS-24Ac achieves the highest reverse intersystem crossing rate constant (krISC) of over 107 s-1 via manipulation of both TSCT and TBCT effects. The solution-processed devices display maximum external quantum efficiencies of 21.73, 12.14 and 4.96% for DPS-24Ac, DPS-25Ac and DPS-OAc, respectively. Overall, this work provides a novel avenue to achieve highly-efficient OLED materials with fast rISC by controlling both TSCT and TBCT effects.

An Unexpected Non-conjugated AIEgen with Discrete Dimer for Pure Intermolecular Through-Space Charge Transfer Emission

Manipulation of the charge transfer in donor-acceptor-type molecules is essential for the design of controllable aggregate luminescent materials. Apart from the traditional through-bond charge transfer (TBCT) systems which suffer from...