The access to electroactive metal–organic frameworks (MOFs) and the ability to manipulate their electrical properties with external stimuli are vital for the realization of MOF-based electronic and photonic devices. To this end, we have constructed a new blue colored pillared-paddlewheel (PPW) MOF, namely BMOF composed of redox-active N,N′-bis(4-pyridyl)-2,6-dipyrrolidyl naphthalenediimide (BPDPNDI) pillars and 1,2,4,5-tetrakis-(4-carboxyphenyl)benzene (TCPB) struts, and grown stable, uniform BMOF films on ZnO substrates via a bottom-up method for device integration and testing. The electrical conductivity (σ) of BMOF films is ca. 6 × 10−5 S m−1 (25 °C), which surges up to 2.3 × 10−3 S m−1 upon infiltration of π-acidic methyl viologen (MV2+) guests, but remains unaffected by large C60 molecules that are size excluded. These results demonstrate for the first time that the conductivity of MOFs can be fine-tuned by complementary guest π-systems that can promote long-range electron delocalization by forming extended π-stacks with the redox-active ligands.

In aprotic solvents, Lewis basic F– anion reduces Lewis acidic Ag(I) cation to Ag(0), forming metallic silver mirrors on the inner surfaces of reaction vessels and luminescent Ag-nanoparticles (AgNPs) in supernatant solutions, which emit blue light upon UV irradiation. The F–-induced formation of silver mirrors and AgNPs was confirmed through X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), fluorescence spectroscopy, and mass spectrometry, whereas the Ag(I)-induced oxidation of F– to Ḟ radical, followed by its conversion to HF2– via H-abstraction and H-bonding, was evident from 19F NMR spectroscopy. This redox reaction is deactivated in water, as the reducing power of hydrated F– diminishes drastically. Less Lewis basic Cl–, Br–, and I– ions do not reduce Ag(I) to Ag(0), instead they can only form Ag(I) halide precipitates irrespective of protic or aprotic solvents. The Ag-coated surfaces, luminescent AgNPs, and Ḟ radicals produced by this unprecedented redox reaction could be exploited as electrodes, light-emitting materials, and radical initiators, respectively.

Multichromophoric dye-sensitized solar cells (DSSCs) comprised of a supramolecular zinc-phthalocyanine⋯peryleneimide (ZnPc⋯PMI) dyad convert light to electrical energy with much higher power conversion efficiency (PCE = 2.3%) and incident-photon-to-current-efficiency (IPCE = ca. 40%) than the devices made of individual dyes.

Depending on functional groups, amphiphilic hexaamide macrocycles self-assemble into closed-shell and open-shell vesicles in polar solvents. In the presence of water, open-shell vesicles morph into closed-shell vesicles, whereas acidification of the medium transforms vesicles into nanotubes and fibers.

A non-interpenetrated square grid metal–organic framework (MOF) comprised of octahedral Zn(II) ions and linear N,N′-di(4-pyridyl)-1,4,5,8-naphthalenediimide (DPNDI) ligands was formed in the presence of noncoordinating perchlorate counterions that occupied the cavities of the porous network by forming CH⋯anion hydrogen bonds with DPNDI ligands, whereas a linear coordination polymer was obtained when Zn(II)-coordinated nitrate ions were present as counterions.

Over the past decade anion–π interaction has emerged as a new paradigm of supramolecular chemistry of anions. Taking advantage of the electronic nature of anion–π interaction, we have expanded its boundaries to charge-transfer (CT) and formal electron transfer (ET) events by adjusting the electron-donating and accepting abilities of anions and π-acids, respectively. To establish that ET, CT, and anion–π interactions could take place between different anions and π-acids as long as their electronic and structural properties are conducive, herein, we introduce 3,4,9,10-perylenediimide (PDI-1) that selectively undergoes thermal ET from strong Lewis basic hydroxide and fluoride anions, but remains electronically and optically silent to poor Lewis basic anions, as ET and CT events are turned OFF. These interactions have been fully characterized by UV/Vis, NMR, and EPR spectroscopies. These results demonstrate the generality of anion-induced ET events in aprotic solvents and further refute a notion that strong Lewis basic hydroxide and fluoride ions can only trigger nucleophilic attack to form covalent bonds instead of acting as sacrificial electron donors to π-acids under appropriate conditions.

The recent emergence of anion−π interactions has added a new dimension to supramolecular chemistry of anions. Yet, after a decade since its inception, actual mechanisms of anion−π interactions remain highly debated. To elicit a complete and accurate understanding of how different anions interact with π-electron-deficient 1,4,5,8-naphthalenediimides (NDIs) under different conditions, we have extensively studied these interactions using powerful experimental techniques. Herein, we demonstrate that, depending on the electron-donating abilities (Lewis basicity) of anions and electron-accepting abilities (π-acidity) of NDIs, modes of anion–NDI interactions vary from extremely weak non-chromogenic anion−π interactions to chromogenic anion-induced charge-transfer (CT) and electron-transfer (ET) phenomena. In aprotic solvents, electron-donating abilities of anions generally follow their Lewis basicity order, whereas π-acidity of NDIs can be fine-tuned by installing different electron-rich and electron-deficient substituents. While strongly Lewis basic anions (OH– and F–) undergo thermal ET with most NDIs, generating NDI•– radical anions and NDI2– dianions in aprotic solvents, weaker Lewis bases (AcO–, H2PO4–, Cl–, etc.) often require the photoexcitation of moderately π-acidic NDIs to generate the corresponding NDI•– radical anions via photoinduced ET (PET). Poorly Lewis basic I– does not participate in thermal ET or PET with most NDIs (except with strongly π-acidic core-substituted dicyano-NDI) but forms anion/NDI CT or anion−π complexes. We have looked for experimental evidence that could indicate alternative mechanisms, such as a Meisenheimer complex or CH···anion hydrogen-bond formation, but none was found to support these possibilities.

Multichromophoric dye-sensitized solar cells (DSCs) based on self-assembled zinc-porphyrin⋯peryleneimide dyads on TiO2 films display more efficient light-to-electrical energy conversion than DSCs based on individual dyes. Higher efficiency of multichromophoric dyes can be attributed to co-sensitization as well as vectorial electron transfer that lead to better electron–hole separation in the device.

Unequivocal structural evidence of noncovalent interactions between π-acidic naphthalenediimides (NDIs) and anions has been elicited by X-ray crystallographic analysis of a zigzag coordination polymer involving Pd(II) ions and linear N,N′-di(4-pyridyl)NDI (DPNDI) ligands. Electrochemical studies show that the DPNDI/TfO− interactions suppress DPNDI's π-acidity, whereas Pd(II)-coordination of DPNDI enhances its π-acidity. The ability of DPNDI to participate in F−-induced electron transfer leading to colorimetric sensing of F− remains intact in the [Pd(II)/DPNDI]n coordination polymer.

Anion-induced electron transfer (ET) to π-electron-deficient naphthalenediimides (NDIs) can be channeled through two distinct pathways by adjusting the Lewis basicity of the anion and the π-acidity of the NDI: (1) When the anion and NDI are a strong electron donor and acceptor, respectively, positioning the HOMO of the anion above the LUMO of the NDI, a thermal anion → NDI ET pathway is turned ON. (2) When the HOMO of a weakly Lewis basic anion falls below the LUMO of an NDI but still lies above its HOMO, the thermal ET is turned OFF, but light can activate an unprecedented anion → 1*NDI photoinduced ET pathway from the anion's HOMO to the photogenerated 1*NDI's SOMO–1. Both pathways generate NDI•– radical anions.

We report the discovery of a supramolecular interaction (anion−π and charge/electron transfer, CT/ET) involving fluoride ion and π-electron deficient colorless naphthalene diimide (NDI) receptors. Strong electronic interactions between lone-pair electrons of F− ion and π*-orbitals of the NDI unit lead to an unprecedented F−→NDI ET event, which produces an orange colored NDI•− radical anion. Further reduction of NDI•− by another F− ion produces a pink colored NDI2− dianion, rendering NDI a colorimetric F− sensor. Preorganization of two NDI units in overlapping positions using folded linkers improves their selectivity and sensitivity for the F− ion significantly, allowing F− detection at nM concentration in 85:15 DMSO/H2O solutions.

Over the past decade anion–π interaction has emerged as a new paradigm of supramolecular chemistry of anions. Taking advantage of the electronic nature of anion–π interaction, we have expanded its boundaries to charge-transfer (CT) and formal electron transfer (ET) events by adjusting the electron-donating and accepting abilities of anions and π-acids, respectively. To establish that ET, CT, and anion–π interactions could take place between different anions and π-acids as long as their electronic and structural properties are conducive, herein, we introduce 3,4,9,10-perylenediimide (PDI-1) that selectively undergoes thermal ET from strong Lewis basic hydroxide and fluoride anions, but remains electronically and optically silent to poor Lewis basic anions, as ET and CT events are turned OFF. These interactions have been fully characterized by UV/Vis, NMR, and EPR spectroscopies. These results demonstrate the generality of anion-induced ET events in aprotic solvents and further refute a notion that strong Lewis basic hydroxide and fluoride ions can only trigger nucleophilic attack to form covalent bonds instead of acting as sacrificial electron donors to π-acids under appropriate conditions.

The access to electroactive metal–organic frameworks (MOFs) and the ability to manipulate their electrical properties with external stimuli are vital for the realization of MOF-based electronic and photonic devices. To this end, we have constructed a new blue colored pillared-paddlewheel (PPW) MOF, namely BMOF composed of redox-active N,N′-bis(4-pyridyl)-2,6-dipyrrolidyl naphthalenediimide (BPDPNDI) pillars and 1,2,4,5-tetrakis-(4-carboxyphenyl)benzene (TCPB) struts, and grown stable, uniform BMOF films on ZnO substrates via a bottom-up method for device integration and testing. The electrical conductivity (σ) of BMOF films is ca. 6 × 10−5 S m−1 (25 °C), which surges up to 2.3 × 10−3 S m−1 upon infiltration of π-acidic methyl viologen (MV2+) guests, but remains unaffected by large C60 molecules that are size excluded. These results demonstrate for the first time that the conductivity of MOFs can be fine-tuned by complementary guest π-systems that can promote long-range electron delocalization by forming extended π-stacks with the redox-active ligands.

Depending on functional groups, amphiphilic hexaamide macrocycles self-assemble into closed-shell and open-shell vesicles in polar solvents. In the presence of water, open-shell vesicles morph into closed-shell vesicles, whereas acidification of the medium transforms vesicles into nanotubes and fibers.

A non-interpenetrated square grid metal–organic framework (MOF) comprised of octahedral Zn(II) ions and linear N,N′-di(4-pyridyl)-1,4,5,8-naphthalenediimide (DPNDI) ligands was formed in the presence of noncoordinating perchlorate counterions that occupied the cavities of the porous network by forming CH⋯anion hydrogen bonds with DPNDI ligands, whereas a linear coordination polymer was obtained when Zn(II)-coordinated nitrate ions were present as counterions.

Multichromophoric dye-sensitized solar cells (DSCs) based on self-assembled zinc-porphyrin⋯peryleneimide dyads on TiO2 films display more efficient light-to-electrical energy conversion than DSCs based on individual dyes. Higher efficiency of multichromophoric dyes can be attributed to co-sensitization as well as vectorial electron transfer that lead to better electron–hole separation in the device.

Multichromophoric dye-sensitized solar cells (DSSCs) comprised of a supramolecular zinc-phthalocyanine⋯peryleneimide (ZnPc⋯PMI) dyad convert light to electrical energy with much higher power conversion efficiency (PCE = 2.3%) and incident-photon-to-current-efficiency (IPCE = ca. 40%) than the devices made of individual dyes.