Cd(II) and Cu(II) coordination polymers based on a multidentate N-donor ligand: syntheses, crystal structures, optical band gaps, and photoluminescence

<div><p>Four Cd(II)- and Cu(II)-containing coordination polymers (CPs) based on a multidentate N-donor ligand and varied dicarboxylate anions, [Cd(3,3′-tmbpt)(<i>p</i>-bdc)]·2.5H₂O (<b>1</b>), [Cd(3,3′-tmbpt)(<i>m</i>-bdc)]·2H₂O (<b>2</b>), [Cu(3,3′-tmbpt)(<i>m</i>-bdc)]·H₂O (<b>3</b>), and [Cu(3,3′-tmbpt)(<i>p</i>-bdc)]·2H₂O (<b>4</b>), where 3,3′-tmbpt = 1 − ((1<i>H</i>-1,2,4-triazol-1-yl)methyl)-3,5-bis(3-pyridyl)-1,2,4-triazole, <i>p</i>-H₂bdc = 1,4-benzenedicarboxylic acid, and <i>m</i>-H₂bdc = 1,3-benzenedicarboxylic acid, have been prepared hydrothermally. The structures of the compounds were determined by single-crystal X-ray diffraction analyses and further characterized by infrared spectra and elemental analyses. Compound <b>1</b> exhibits a 3-D twofold interpenetrating framework with a 6⁵·8 CdSO₄ topology. Compound <b>2</b> is a 2-D layer containing meso-helical chains with a 4⁴·6² sql topology. Compound <b>3</b> shows a 1-D → 3-D interdigitated architecture while <b>4</b> displays a 2-D → 3-D interdigitated architecture. The structural differences of the compounds indicate that the dicarboxylate anions and the central metal ions play important roles in the resulting structures of CPs. Optical band gaps and solid-state photoluminescent properties have also been studied.</p></div

Computational Design of Host Materials Suitable for Green-(Deep) Blue Phosphors through Effectively Tuning the Triplet Energy While Maintaining the Ambipolar Property

We theoretically designed a series of ambipolar host materials (<b>1</b>–<b>8</b>) which incorporate phosphine oxide and carbazole groups to the two ends of diphenyl (DP)-like bridges by para- and meta-connections, respectively. Density functional theory calculations were performed to investigate the influence of altering the DP-like bridges of these molecules on electronic structures and properties, and further to predict their performances as host materials in organic light-emitting diodes. The investigated results show the highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) of <b>1</b>–<b>8</b>, distributed at the phenylcarbazole and the DP-like bridge, are responsible for hole and electron injection properties, respectively. The difference in the energies of HOMOs or LUMOs for <b>1</b>–<b>8</b> may be derived from different degrees of conjugation effect and electrostatic induction with altering the DP-like bridges of <b>1</b>–<b>8</b>. The singlet states (S₁), arising from the HOMO → LUMO transition, have intramolecular charge transfer character, which determines the small and different values of S₁ energies. On the other hand, altering the DP-like bridges brings a great effect on triplet exciton distributions, and consequently different triplet energies. The different singlet/triplet energies for <b>1</b>–<b>8</b> make hosts <b>1</b>–<b>8</b> suitable for four reference guests with green/deep-blue light when scientists consider the matching of host and guest in singlet/triplet energies for efficient energy transfer

Syntheses, structures, and photocatalysis of five inorganic–organic hybrid compounds constructed from Keggin polyoxometalate clusters and multidentate N-donor ligands

<div><p>Five inorganic–organic hybrid compounds have been prepared under hydrothermal conditions and characterized by single-crystal X-ray diffraction analyses, infrared spectra, elemental analyses, powder X-ray diffraction, and thermogravimetric analyses. In <b>1</b>, each 2,2ʹ-tmbpt ligand links two Cu(II) ions to generate a highly undulated chain. The chains are further bridged by [SiW₁₂O₄₀]^4‒ anions to form a layer. Compound <b>2</b> exhibits a 3-D (3,4,5)-connected framework with large channels, in which [SiW₁₂O₄₀]^4‒ anions are tetradentate linkages. In <b>3</b>, each 2,4ʹ-tmbpt links three Cu(II) ions to form 2-D layers, which are further linked by [SiW₁₂O₄₀]^4‒ to yield a 3-D (3,4)-connected framework. In <b>4</b>, each 4,4ʹ-tmbpt connects three Cu(II) ions to generate 1-D double chains. In <b>5</b>, [PW₁₂O₄₀]^3‒ link Cu(II) ions to generate 1-D chains. Compounds <b>1</b>‒<b>5</b> exhibit photocatalytic activities for degradation of methylene blue and rhodamine B.</p></div

Large Nonlinear Optical Responses of Dimers Bearing a Donor and Acceptor: Long, Intradimer Multicenter Bonding

Unusual long, multicenter dimers bearing a large electron donor and acceptor have been the subject of great interest over the last decades due to their better conducting, superconducting, magnetic, or other physical properties. Two-electron, multicenter bonding between two interplanar fragments has been recently recognized as a novel and important bonding interaction. Herein, the [TTF]­[TCNE], [TTF]­[TCNQ], [TTF]­[TCNP], and [TTF]­[TCNB] dimeric species have been studied by quantum mechanics methods with the view of assessing their interactions and first hyperpolarizabilities. It is found that the stabilities of the dimers primarily originate from the electrostatic bonding component. Although to a lesser extent, long, multicenter interactions due to the overlap of the molecular orbitals of the monomers are important also in the stability of these systems. Significantly, a severe hyperpolarizability decrease with changing the acceptor monomers of the dimeric species is qualitatively explained in terms of change in their charge transfer patterns. It indicates that the first hyperpolarizabilities of these dimers can be optimized by controlling their relative acceptor monomers. We believe that these results shall provide important information for further exploration of long, multicenter dimers with versatile and fascinating nonlinear optical properties

Synthesis, structure, and properties of a new Co(II) diphosphonate based on auxiliary ligand 2,2'-bipyridine

<p>The example of Co(II)-<i>N</i>-heterocyclic complex based on 1-hydroxyethylidenediphosphonic acid (H₅L = CH₃C(OH)(PO₃H₂)₂), namely [Co₂(H₃L)₂(2,2′-bipy)₂] <b>1</b>, has been solvothermally isolated using the second ligand 2,2'-bipyridine (2,2'-bipy) and characterized by powder X-ray diffraction (PXRD), elemental analysis, IR, and thermal gravimetric analyses. The single-crystal X-ray diffractions show that complex <b>1</b> possesses a 0-D structure built from binuclear unit [Co₂(O–P–O)₂] by μ₂-(O–P–O) bridge. Then, H-bonding and π–π stacking interactions further expand this 0-D structure into a 3-D supramolecular framework. Fluorescent measurements reveal that the maximum emission peak is centered at 421.5 nm, mainly deriving from intraligand π*–π transition state of the second ligand 2,2'-bipy (λ_em = 419.5 nm, λ_ex = 235 nm). Magnetism data indicate that <b>1</b> exhibits ferromagnetic behavior within binuclear Co(II) unit via μ₂-(O–P–O) bridge in <i>syn</i>-<i>anti</i> mode.</p

Quantum Chemical Insight into the LiF Interlayer Effects in Organic Electronics: Reactions between Al Atom and LiF Clusters

It is well known that the aluminum cathode performs dramatically better when a thin lithium fluoride (LiF) layer inserted in organic electronic devices. The doping effect induced by the librated Li atom via the chemical reactions producing AlF₃ as byproduct was previously proposed as one of possible mechanisms. However, the underlying mechanism discussion is quite complicated and not fully understood so far, although the LiF interlayer is widely used. In this paper, we perform theoretical calculations to consider the reactions between an aluminum atom and distinct LiF clusters. The reaction pathways of the Al–(LiF)<i>_n</i> (<i>n</i> = 2, 4, 16) systems were discovered and the energetics were theoretically evaluated. The release of Li atom and the formation of AlF₃ were found in two different chemical reaction routes. The undissociated Al–(LiF)<i>_n</i> systems have chances to change to some structures with loosely bound electrons. Our findings about the interacted Al–(LiF)<i>_n</i> systems reveal new insights into the LiF interlayer effects in organic electronics applications

Theoretical Study on a Novel Series of Fullerene-Containing Organometallics Fe(η⁵-C₅₅X₅)₂ (X = CH, N, B) and Their Large Third-Order Nonlinear Optical Properties

Geometry structures, electronic spectra, and third-order nonlinear optical (NLO) properties of Fe(η5-C55X5)2 (X = CH, N, B) have first been investigated by time-dependent density functional theory. We analyzed the intramolecular interactions between ferrocene and the C50 moiety. The calculated electronic absorption spectrum indicates that the short wavelength transitions are ascribed to the C50 moiety mixed charge transfer transition of ferrocene itself, while the low energy excitation transitions are ascribed to the unique charge transfer transition from ferrocene to C50 moiety in these systems. The third-order polarizability γ values based on sum of states (SOS) method show that this class of ferrocene/fullerene hybrid molecule possesses a remarkably large third-order NLO response, especially for Fe(η5-C55B5)2 with the static third-order polarizability (γav) computed to be −10410 × 10−36 esu and the intrinsic second hypepolarizability to be 0.250. Thus, these complexes have the potential to be used for excellent third-order nonlinear optical materials. Analysis of the major contributions to the γav value suggest that the charge transfer from ferrocene to C50 moiety along the z-axis (through Fe atom and the centers of two hybrid fullerenes) play the key role in the NLO response. Furthermore, boron substitution is an effective way of enhancing the optical nonlinearity compared to CH and N substitution, owing to smaller energy gap and better conjugation through the whole molecule

Monometallic Catalytic Models Hosted in Stable Metal–Organic Frameworks for Tunable CO₂ Photoreduction

The photocatalytic reduction of CO2 to energy carriers has emerged as one of the most promising strategies to alleviate the energy crisis and CO2 pollution, for which the development of catalyst was considered as the determining factor for the accomplishment of this conversion process. In this study, three stable and isostructural metal–organic frameworks (denoted as MOF-Ni, MOF-Co, and MOF-Cu) have been synthesized and used as heterogeneous catalysts in photocatalytic CO2 reduction reaction (CO2RR). It is worth noting that the MOF-Ni exhibited very high selectivity of 97.7% for photoreducing CO2 to CO, which has exceeded most of the reported MOF-based catalysts in the field. Significantly, the MOFs associated with a monometallic catalytic center offer a simple and precise structural model which allows us to understand more definitively the specific effects of different metal-ion species on photoreduction of CO2 as well as the reactive mechanism

Monometallic Catalytic Models Hosted in Stable Metal–Organic Frameworks for Tunable CO₂ Photoreduction

The photocatalytic reduction of CO2 to energy carriers has emerged as one of the most promising strategies to alleviate the energy crisis and CO2 pollution, for which the development of catalyst was considered as the determining factor for the accomplishment of this conversion process. In this study, three stable and isostructural metal–organic frameworks (denoted as MOF-Ni, MOF-Co, and MOF-Cu) have been synthesized and used as heterogeneous catalysts in photocatalytic CO2 reduction reaction (CO2RR). It is worth noting that the MOF-Ni exhibited very high selectivity of 97.7% for photoreducing CO2 to CO, which has exceeded most of the reported MOF-based catalysts in the field. Significantly, the MOFs associated with a monometallic catalytic center offer a simple and precise structural model which allows us to understand more definitively the specific effects of different metal-ion species on photoreduction of CO2 as well as the reactive mechanism

Monometallic Catalytic Models Hosted in Stable Metal–Organic Frameworks for Tunable CO₂ Photoreduction

The photocatalytic reduction of CO2 to energy carriers has emerged as one of the most promising strategies to alleviate the energy crisis and CO2 pollution, for which the development of catalyst was considered as the determining factor for the accomplishment of this conversion process. In this study, three stable and isostructural metal–organic frameworks (denoted as MOF-Ni, MOF-Co, and MOF-Cu) have been synthesized and used as heterogeneous catalysts in photocatalytic CO2 reduction reaction (CO2RR). It is worth noting that the MOF-Ni exhibited very high selectivity of 97.7% for photoreducing CO2 to CO, which has exceeded most of the reported MOF-based catalysts in the field. Significantly, the MOFs associated with a monometallic catalytic center offer a simple and precise structural model which allows us to understand more definitively the specific effects of different metal-ion species on photoreduction of CO2 as well as the reactive mechanism