Superalkali-alkaline earthide ion pairs of δ+(AM-HMHC)-AM'δ- (AM = Li, Na and K; AM' = Be, Mg and Ca) possessing large NLO responses and excellent electronic stabilities and alkalide characteristics: a DFT study.

To identify superalkali-alkaline earthide ion pairs, it's theoretically shown that, as a novel class of excess electron superalkali compounds, both chair and boat forms of (AM-HMHC)-AM' (AM = Li, Na, and K; AM' = Be, Mg, and Ca; HMHC = 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane) are good candidates. An attractive superalkali-alkaline earthide ion pair in δ+(AM-HMHC)-AM'δ- is firstly exhibited, which possesses alkaline-earthide characteristics and nonlinear optical response superior to similar M+(calix[4]pyrrole)M'- (M = Li, Na, and K; M' = Be, Mg, and Ca) with high stability. The electronic and vibrational second order hyperpolarizabilities and the frequency-dependent first hyperpolarizabilities of δ+(AM-HMHC)-AM'δ- are presented. For each pair of (AM-HMHC)-AM', the boat conformation is preferred to its chair one in the case of Hyper-Rayleigh scattering response (ßHRS). These alkaline earthides suggest prominently high ßHRS up to 2.59 × 104 a.u. (boat forms of δ+(Na-HMHC)-Caδ-). We expect that this work will inspire the preparation and characterization of these new alkaline earthides as high-performance NLO materials.

Switching from an electride-like molecule to the molecular electride K-F6C6H6 driven by an oriented external electric field.

The exploration of innovative molecular switches has resulted in large developments in the field of molecular electronics. Focusing on a single molecular switch with different forms exhibiting different electride features, potassium-atom-doped all-cis 1,2,3,4,5,6-hexafluorocyclohexane K-F6C6H6 was studied theoretically. It was found that an oriented external electric field can drive excess electron transfer from the region outside of the K atom to that outside of F6C6H6. Subsequently, the electride-like molecule K-F6C6H6 (1) switches into the molecular electride K-F6C6H6e- (3) through another electride-like molecule K-F6C6H6 (2). The static first hyperpolarizabilities (ß0) are increased over 12- and 5-fold when moving from 1 to 2 and 3, respectively. The rise of each ß0 value constitutes an order of magnitude improvement. Between them, the different ß0 values suggest that K-F6C6H6 is a good candidate for use as a multiple-response nonlinear optics switch. The order of the ß0 values of 1-4 for M-F6C6H6 (M = Li and Na) coincide with that of K-F6C6H6, also exhibiting a switch effect.

Novel inorganic aromatic mixed-valent superalkali electride CaN3Ca: an alkaline-earth-based high-sensitivity multi-state nonlinear optical molecular switch.

Focusing on innovative high-performance single-pole double-throw nonlinear optical (NLO) molecular switches, two C3v configurations (1 and 3) and one D3h configuration (2) of bipyramidal CaN3Ca have been obtained by using quantum mechanical methods. Not only are 1, 2, and 3 alkaline-earth-based aromatic superalkalis, but they are also interesting electrides. The salt-like electronic structures of e-Ca2+N33-Ca2+ (1) and Ca2+N33-Ca2+e- (3) with localized redox centres are rare inorganic Robin-Day class II-type structures, and e0.5-Ca2+N33-Ca2+e0.5- (2) with a delocalized structure is a class III-type mixed-valent superalkali electride. Under a small external electric field of ±0.0110 a.u. (0.565 V Å-1), the short-distance hopping of Ca atoms in CaN3Ca from the D3h configuration with in-plane aromaticity to each C3v configuration with out-of-plane aromaticity brings about the long-range transfer of half an electron from one Ca atom to another. And, subsequently, a large dipole moment (µ0) and remarkable static first hyperpolarizability (ß0) occur. µz and ßzzz range from 0 (D3h, off form) to -12.1 or 12.1 D (C3v, on forms) and from 0 (D3h, off form) to -19 428 or 19 428 a.u. (C3v, on forms), respectively. These extremely large differences in µz and ßzzz values between the D3h and each of the C3v configurations confirm the potential of these inorganic aromatic Robin-Day-type superalkali electrides for applications in high-sensitivity multi-state nonlinear optical switches.

Electric field induced intra-molecular self-redox: superalkali Li3N3Mg as a candidate for NLO molecular switches.

A novel intra-molecular self-redox switch, Li3N3Mg, is constructed theoretically. Our investigation showed that a suitably oriented external electric field (OEEF) can drive a long-range excess electron transfer from Mg atoms to Li3 rings. And subsequently, an interesting intra-molecular self-redox from Li32+N33-Mg+ to Li3+N33-Mg2+ accompanying the large different electronic static first hyperpolarizability (ß) is exhibited. The increase of the ß value constitutes an order of magnitude improvement from Li32+N33-Mg+ (34 986 a.u.) to Li3+N33-Mg2+ (101 225 a.u.), which indicates that Li3N3Mg is a good candidate for a self-redox NLO molecular switch.

Preparation, Structure, Photoluminescent and Semiconductive Properties, and Theoretical Calculation of a Novel Cadmium Complex with Mixed Ligands.

A novel cadmium complex with mixed ligands [Cd(2,2'-biim)(4,4'-bipy)(H2O)(ClO4)] (ClO4)n (1) (2,2'-biim = 2,2'-biimidazole; 4,4'-bipy = 4,4'-bipyridine) has been synthesized through hydrothermal reaction and its crystal structure was determined by single-crystal X-ray diffraction technique. Single-crystal X-ray diffraction analyses revealed that complex 1 crystallizes in the space group Pna21 of the orthorhombic system and exhibits a one-dimensional zigzag chain structure consisting of [Cd(2,2'-biim)(4,4'-bipy)(H2O)(ClO4)]n n+ cationic chains and isolated ClO4 - anions. Powder photoluminescent characterization reveals that complex 1 has an emission in the green region of the spectrum. Time-dependent density functional theory (TDDFT) calculation showed that the nature of the photoluminescence of complex 1 is originated from the ligand-to-ligand charge transfer (LLCT; from the HOMO of the perchlorate anions to the LUMO of the 4,4'-bipy ligand). A wide optical band gap of 3.25 eV was found by the solid-state UV/vis diffuse reflectance spectrum.

In Situ Preparation, Structure, Photoluminescence and Theoretical Study of an Unusual Bismuth Complex.

A novel bismuth photoluminescent material, (N,N'-dimethyl-2,2'-bipy)2(Bi2Cl10) · 2H2O (1) (bipy = bipyridine), with the N,N'-dimethyl-2,2'-bipy2+ moiety obtained in situ, has been synthesized under solvothermal conditions and characterized by single-crystal X-ray diffraction. Compound 1 is characterized by an isolated structure, consisting of N,N'-dimethyl- 2,2'-bipy2+ cations, Bi2Cl10 4- anions and lattice water molecules. Photoluminescence experiments with solidstate samples discover that compound 1 exhibits a strong emission in the green region. Time-dependent density functional theory (TDDFT) calculation reveals that the essence of the photoluminescence of 1 can be assigned to the combination of the metal-to-ligand charge transfer (MLCT) (from the HOMO of the bismuth ion to the LUMO of the N,N'-dimethyl-2,2'-bipy2+ moiety) and the ligand-to-ligand charge transfer (LLCT) (from the HOMO of the chloride ions to the LUMO of the N,N'-dimethyl-2,2'-bipy2+ moiety).

Controlled self-assembly and photovoltaic characteristics of porphyrin derivatives on a silicon surface at solid-liquid interfaces.

Two meso-tetraphenylporphyrin (H2TPP) derivatives with different central metal ions, namely ZnTPP, CuTPP, were synthesized, and characterized by a series of spectroscopic methods. Their self-assembly behaviors in mixed solvents without surfactant were systematically investigated. The morphology of the thus produced nanoarchitectures could be efficiently controlled. Nanoslices can be manufactured when a volume of cyclohexane is involved, octahedrons can be produced when a mixed solvent of chloroform and isopropanol is employed, while four-leaf clover-shaped structures can be produced with a large volume of methanol injected. The nanostructures have been characterized by electronic absorption, scanning electron microscopy (SEM) and photoelectric conversion techniques. The internal structures of the nanostructures are well described by XRD. The nanostructures exhibit a power conversion under illumination intensity of 2.3 mW cm(-2). The present result appears to represent an effort toward controlling the morphology of self-assembled nanostructures of porphyrin derivatives via synthesis through introduction of metal-ligand and solvent interaction. Nevertheless, the fundamental study will be helpful to understand photoinduced energy/charge transport in an organic interface and this might also serve as promising building blocks for nanoscale power sources for potential application in solar energy technologies and organic electronics and optoelectronics.

OEEF-Driven Intramolecular Self-Redox of Superalkali Rb3BeB6Be'Rb'3: A High-Performance Candidate for NLO Molecular Switch.

To provide a novel intramolecular self-redox switch, a boron-based sandwich-like complex Rb3BeB6Be'Rb'3 is achieved by using theoretical computations. An applicable oriented external electric field (OEEF) can result in the occurrence of intramolecular self-redox (IMSR) with a long-range electron transfer from tetrahedral Be'Rb'3 to Rb3Be and subsequently [Rb3Be]3+[B6]6-[Be'Rb'3]3+ (D3d) changes to [Rb3Be]2+[B6]6-[Be'Rb'3]4+ (C3v), accompanying high-performance NLO switchable effect for both static and dynamic first hyperpolarizability (ß0). [Rb3Be]3+[B6]6-[Be'Rb'3]3+ (off-form) owns zero of dipole moment (µ0) and ß0, while [Rb3Be]2+[B6]6-[Be'Rb'3]4+ (on-form) exhibits a µ0 of 3.36 D and a ß0e of 2.18 × 105 au. The different dynamic first hyperpolarizabilities between [Rb3Be]3+[B6]6-[Be'Rb'3]3+ and [Rb3Be]2+[B6]6-[Be'Rb'3]4+ are also significant. This indicates that Rb3BeB6Be'Rb'3 is a potential candidate for an IMSR NLO switch.

Intercage electron transfer driven by electric field in Robin-Day-type molecules.

A new class of isomers, namely, intercage electron-transfer isomers, is reported for fluorinated double-cage molecular anion e(-)@C(20)F(18)(NH)(2)C(20)F(18) with C(20)F(18) cages: 1 with the excess electron inside the left cage, 2 with the excess electron inside both cages, and 3 with the excess electron inside the right cage. Interestingly, the C(20)F(18) cages may be considered as two redox sites existing in a rare nonmetal mixed-valent (0 and -1) molecular anion. The three isomers with two redox sites may be the founding members of a new class of mixed-valent compounds, namely, nonmetal Robin-Day Class II with localized redox centers for 1 and 3, and Class III with delocalized redox centers for 2. Two intercage electron-transfers pathways involving transfer of one or half an excess electron from one cage to the other are found: 1) Manipulating the external electric field (-0.001 a.u. for 1→3 and -0.0005 a.u. for 1→2) and 2) Exciting the transition from ground to first excited state and subsequent radiationless transition from the excited state to another ground state for 1 and 3. For the exhibited microscopic electron-transfer process 1→3, 2 may be the transition state, and the electron-transfer barrier of 6.021 kcal mol(-1) is close to the electric field work of 8.04 kcal mol(-1).

Theoretical investigation of the structures, stabilities, and NLO responses of calcium-doped pyridazine: alkaline-earth-based alkaline salt electrides.

Currently, whether alkaline-earth-doped compounds with electride characteristics are novel candidates for high-performance nonlinear optical (NLO) materials is unknown. In this paper, using quantum chemical computations, we show that: when doping calcium atoms into a family of alkaline-substituted pyridazines, alkaline-earth-based alkaline salt electrides M-H3C4N2⋯Ca (M=H, Li, and K) with distended excess electron clouds are formed. Interestingly, from the triplet to the singlet state, the chemical valence of calcium atom changes from +1 to 0, and the dipole moment direction (µ0) of the molecule reverses for each M-H3C4N2⋯Ca. Changing pyridazine from without (H4C4N2⋯Ca) to with one alkaline substituent (M-H3C4N2⋯Ca, M=Li and K), the ground state changes from the triplet to the singlet state. The alkaline earth metal doping effect (electride effect) and alkaline salt effect on the static first hyperpolarizabilities (ß0) demonstrates that (1) the ß0 value is increased approximately 1371-fold from 2 (pyridazine, H4C4N2) to 2745au (Ca-doped pyridazine, H4C4N2⋯Ca), (2) the ß0 value is increased approximately 1146-fold from 2 in pyridazine (H4C4N2) to 2294au in an Li-substituted pyridazine (Li-H3C4N2), and (3) the ß0 value is increased 324-(M=Li) and 106-(M=K) fold from 826 (MLi) and 2294au (MK) to 268,679 (M=Li) and 245,878au (M=K), respectively, from the alkalized pyridazine (M-H3C4N2) to the Ca-doped pyridazine (M-H3C4N2⋯Ca). These results may provide a new means for designing high-performance NLO materials.