Agus Aris Munandar, Ibukota Majapahit; Masa Jaya dan Pencapaian. Depok: Komunitas Bambu, 2008, X + 161 Pp. ISBN 979-37-31-39-7. Price: IDR 34,000 (Soft Cover).

Palladium-catalyzed cross-coupling reactions between chlorinated 1,3,5-triazines (TZ) and tetrathiafulvalene (TTF) trimethyltin derivatives afford mono- and <i>C</i>₃ symmetric tris­(TTF)-triazines as donor–acceptor compounds in which the intramolecular charge transfer (ICT) is modulated by the substitution scheme on TTF and TZ and by chemical or electrochemical oxidation. The TTF-TZ-Cl₂ and (SMe)₂TTF-TZ-Cl₂ derivatives show fully planar structures in the solid state as a consequence of the conjugation between the two units. Electrochemical and photophysical investigations, supported by theoretical calculations, clearly demonstrate that the lowest excited state can be ascribed to the intramolecular charge transfer (ICT) π­(TTF)→π*­(TZ) transition. The tris­(TTF) compound [(SMe)₂TTF]₃-TZ shows fluorescence when excited in the ICT band, and the emission is quenched upon oxidation. The radical cations TTF^+• are easily observed in all of the cases through chemical and electrochemical oxidation by steady-state absorption experiments. In the case of [(SMe)₂TTF]₃-TZ, a low energy band at 5000 cm^–1, corresponding to a coupling between TTF^+• and TTF units, is observed. A crystalline radical cation salt with the TTF-TZ-Cl₂ donor and PF₆^– anion, prepared by electrocrystallization, is described

Tetrathiafulvalene-Triazine-Dipyridylamines as Multifunctional Ligands for Electroactive Complexes: Synthesis, Structures, and Theoretical Study

The electroactive ligands (2,4-bis-tetrathiafulvalene­[6-(dipyridin-2′-ylamino)]-1,3,5-triazine) TTF₂-tz-dpa (<b>1</b>) and (2-tetrathiafulvalene­[4,6-bis-(dipyridin-2′-ylamino)]-1,3,5-triazine) TTF-tz-dpa₂ (<b>2</b>) have been synthesized by palladium cross-coupling catalysis, and the single crystal X-ray structure for <b>1</b> was determined. In the solid state the TTF and triazine units are practically coplanar and short intermolecular S···S contacts are established. Two neutral and one tetracationic Zn­(II) complexes, formulated as (TTF₂-tz-dpa)­ZnCl₂ (<b>3</b>), [ZnCl₂(TTF-tz-dpa₂)­Zn­(H₂O)­Cl₂] (<b>4</b>), and {[(H₂O)₂Zn­(TTF-tz-dpa₂)]­(ClO₄)₂}₂ (<b>5</b>) have been crystallized and analyzed by single crystal X-ray analysis. A peculiar feature is the evidence for anion-π interactions, as shown by the short Cl···triazine and O­(perchlorate)···triazine distances of 3.52 and 3.00 Å, respectively. A complex set of intermolecular π···π, S···S, and hydrogen bonding interactions sustain the supramolecular organizations of the complexes in the solid state. Electronic absorption spectra provide evidence for the intramolecular charge transfer from TTF to triazine, also supported by time-dependent density functional theory (TD DFT) calculations

Tetrathiafulvalene-Triazine-Dipyridylamines as Multifunctional Ligands for Electroactive Complexes: Synthesis, Structures, and Theoretical Study

The electroactive ligands (2,4-bis-tetrathiafulvalene­[6-(dipyridin-2′-ylamino)]-1,3,5-triazine) TTF₂-tz-dpa (<b>1</b>) and (2-tetrathiafulvalene­[4,6-bis-(dipyridin-2′-ylamino)]-1,3,5-triazine) TTF-tz-dpa₂ (<b>2</b>) have been synthesized by palladium cross-coupling catalysis, and the single crystal X-ray structure for <b>1</b> was determined. In the solid state the TTF and triazine units are practically coplanar and short intermolecular S···S contacts are established. Two neutral and one tetracationic Zn­(II) complexes, formulated as (TTF₂-tz-dpa)­ZnCl₂ (<b>3</b>), [ZnCl₂(TTF-tz-dpa₂)­Zn­(H₂O)­Cl₂] (<b>4</b>), and {[(H₂O)₂Zn­(TTF-tz-dpa₂)]­(ClO₄)₂}₂ (<b>5</b>) have been crystallized and analyzed by single crystal X-ray analysis. A peculiar feature is the evidence for anion-π interactions, as shown by the short Cl···triazine and O­(perchlorate)···triazine distances of 3.52 and 3.00 Å, respectively. A complex set of intermolecular π···π, S···S, and hydrogen bonding interactions sustain the supramolecular organizations of the complexes in the solid state. Electronic absorption spectra provide evidence for the intramolecular charge transfer from TTF to triazine, also supported by time-dependent density functional theory (TD DFT) calculations

Tetrathiafulvalene-Triazine-Dipyridylamines as Multifunctional Ligands for Electroactive Complexes: Synthesis, Structures, and Theoretical Study

The electroactive ligands (2,4-bis-tetrathiafulvalene­[6-(dipyridin-2′-ylamino)]-1,3,5-triazine) TTF₂-tz-dpa (<b>1</b>) and (2-tetrathiafulvalene­[4,6-bis-(dipyridin-2′-ylamino)]-1,3,5-triazine) TTF-tz-dpa₂ (<b>2</b>) have been synthesized by palladium cross-coupling catalysis, and the single crystal X-ray structure for <b>1</b> was determined. In the solid state the TTF and triazine units are practically coplanar and short intermolecular S···S contacts are established. Two neutral and one tetracationic Zn­(II) complexes, formulated as (TTF₂-tz-dpa)­ZnCl₂ (<b>3</b>), [ZnCl₂(TTF-tz-dpa₂)­Zn­(H₂O)­Cl₂] (<b>4</b>), and {[(H₂O)₂Zn­(TTF-tz-dpa₂)]­(ClO₄)₂}₂ (<b>5</b>) have been crystallized and analyzed by single crystal X-ray analysis. A peculiar feature is the evidence for anion-π interactions, as shown by the short Cl···triazine and O­(perchlorate)···triazine distances of 3.52 and 3.00 Å, respectively. A complex set of intermolecular π···π, S···S, and hydrogen bonding interactions sustain the supramolecular organizations of the complexes in the solid state. Electronic absorption spectra provide evidence for the intramolecular charge transfer from TTF to triazine, also supported by time-dependent density functional theory (TD DFT) calculations

A Series of Tetrathiafulvalene-Based Lanthanide Complexes Displaying Either Single Molecule Magnet or LuminescenceDirect Magnetic and Photo-Physical Correlations in the Ytterbium Analogue

The reaction between (4,5-bis­(2-pyridyl-<i>N</i>-oxidemethylthio)-4′,5′)-ethylenedithiotetrathiafulvene (<b>L</b>^<b>1</b>) or -methyldithiotetrathiafulvene (<b>L</b>^<b>2</b>) ligands and Ln­(hfac)₃·<i>n</i>H₂O precursors (Ln^III = Pr, Tb, Dy, Er, and Yb) leads to the formation of seven dinuclear complexes of formula [Ln₂(hfac)₆(H₂O)_<i>x</i>(<b>L</b>^<b>y</b>)₂] (<i>x</i> = 2 and <i>y</i> = 1 for Ln^III = Pr (<b>1</b>); <i>x</i> = 0 and <i>y</i> = 1 for Ln^III = Tb (<b>2</b>), Dy (<b>3</b>), Er (<b>4</b>) and Yb (<b>5</b>); <i>x</i> = 0 and <i>y</i> = 2 for Ln^III = Tb (<b>6</b>) and Dy (<b>7</b>)). Their X-ray structures reveal that the coordination environment of each Ln^III center is filled by two <i>N</i>-oxide groups coming from two different ligands <b>L</b>^<b>y</b>. UV–visible absorption properties have been experimentally measured and rationalized by TD-DFT calculations. The temperature dependences of static magnetic measurements have been fitted. The ground state corresponds to the almost pure |<i>M</i>_<i>J</i> = ±13/2⟩ while the first excited state (±0.77|±11/2⟩ ± 0.50|±3/2⟩ ± 0.39|±5/2⟩) is located at 19 cm^–1 and 26.9 cm^–1 respectively for <b>3</b> and <b>7</b>. Upon irradiation at 77 K and at room temperature, in the range 25 000–20 835 cm^–1, both compounds <b>4</b> and <b>5</b> display a metal-centered luminescence attributed to ⁴I_13/2 → ⁴I_15/2 (6660 cm^–1) and ²F_5/2 → ²F_7/2 (9972 cm^–1) transitions, respectively. Emission spectroscopy provides a direct probe of the |±5/2⟩ ground state multiplet splitting, which has been confronted to magnetic data. The energy separation of 225 cm^–1 between the ground state and the first excited level (<i>M</i>_<i>J</i> = ±3/2) fits exactly the second emission line (234 cm^–1). While no out-phase-signal is detected for <b>3</b>, the change of ligand <b>L</b>^<b>1</b> → <b>L</b>^<b>2</b> induces a change of coordination sphere symmetry around the Dy^III increasing the energy splitting between the ground and first excited states, and <b>7</b> displays a single molecule magnet behavior

In Solution Sensitization of Er(III) Luminescence by the 4-Tetrathiafulvalene-2,6-pyridinedicarboxylic Acid Dimethyl Antenna Ligand

In the [Er­(hfac)₃(<b>L</b>)]₂ complex (<b>1</b>) (<b>L</b> = 4-tetrathiafulvalene-2,6-pyridinecarboxylic acid dimethyl ester), the Er­(III) ion is bonded to the tridentate coordination site. Electrochemical and photophysical measurements in solution reveal that the tetrathiafulvalene moiety is a versatile antenna for erbium luminescence sensitization at 6540 cm^–1 upon excitation in the low-energy charge transfer transition (donor to acceptor charge transfer) at 16600 cm^–1 assigned via time-dependent density functional theory calculations

Highly Reactive Diazenyl Radical Species Evidenced during Aryldiazonium Electroreduction

We report the experimental reassessment of the widely admitted concerted reduction mechanism for diazonium electroreduction. Ultrafast cyclic voltammetry was exploited to demonstrate the existence of a stepwise pathway, and real-time spectroelectrochemistry experiments allowed visualization of the spectral signature of an evolution product of the phenyldiazenyl radical intermediate. Unambiguous identification of the diazenyl species was achieved by radical trapping followed by X-ray structure resolution. The electrochemical generation of this transient under intermediate energetic conditions calls into question our comprehension of the layer structuration when surface modification is achieved via the diazonium electrografting technique as this azo-containing intermediate could be responsible for the systematic presence of azo bridges in nanometric films

In Solution Sensitization of Er(III) Luminescence by the 4-Tetrathiafulvalene-2,6-pyridinedicarboxylic Acid Dimethyl Antenna Ligand

In the [Er­(hfac)₃(<b>L</b>)]₂ complex (<b>1</b>) (<b>L</b> = 4-tetrathiafulvalene-2,6-pyridinecarboxylic acid dimethyl ester), the Er­(III) ion is bonded to the tridentate coordination site. Electrochemical and photophysical measurements in solution reveal that the tetrathiafulvalene moiety is a versatile antenna for erbium luminescence sensitization at 6540 cm^–1 upon excitation in the low-energy charge transfer transition (donor to acceptor charge transfer) at 16600 cm^–1 assigned via time-dependent density functional theory calculations

Highly Reactive Diazenyl Radical Species Evidenced during Aryldiazonium Electroreduction

We report the experimental reassessment of the widely admitted concerted reduction mechanism for diazonium electroreduction. Ultrafast cyclic voltammetry was exploited to demonstrate the existence of a stepwise pathway, and real-time spectroelectrochemistry experiments allowed visualization of the spectral signature of an evolution product of the phenyldiazenyl radical intermediate. Unambiguous identification of the diazenyl species was achieved by radical trapping followed by X-ray structure resolution. The electrochemical generation of this transient under intermediate energetic conditions calls into question our comprehension of the layer structuration when surface modification is achieved via the diazonium electrografting technique as this azo-containing intermediate could be responsible for the systematic presence of azo bridges in nanometric films

Crystalline Arrays of Pairs of Molecular Rotors: Correlated Motion, Rotational Barriers, and Space-Inversion Symmetry Breaking Due to Conformational Mutations

The rod-like molecule bis­((4-(4-pyridyl)­ethynyl)­bicyclo[2.2.2]­oct-1-yl)­buta-1,3-diyne, <b>1</b>, contains two 1,4-bis­(ethynyl)­bicyclo[2.2.2]­octane (BCO) chiral rotators linked by a diyne fragment and self-assembles in a one-dimensional, monoclinic <i>C</i>2/<i>c</i> centrosymmetric structure where two equilibrium positions with large occupancy imbalance (88% versus 12%) are identified on a single rotor site. Combining variable-temperature (70–300 K) proton spin–lattice relaxation, ¹H <i>T</i>₁^–1, at two different ¹H Larmor frequencies (55 and 210 MHz) and DFT calculations of rotational barriers, we were able to assign two types of Brownian rotators with different activation energies, 1.85 and 6.1 kcal mol^–1, to the two ¹H spin–lattice relaxation processes on the single rotor site. On the basis of DFT calculations, the low-energy process has been assigned to adjacent rotors in a well-correlated synchronous motion, whereas the high-energy process is the manifestation of an abrupt change in their kinematics once two blades of adjacent rotors are seen to rub together. Although crystals of <b>1</b> should be second harmonic inactive, a large second-order optical response is recorded when the electric field oscillates in a direction parallel to the unique rotor axle director. We conclude that conformational mutations by torsional interconversion of the three blades of the BCO units break space-inversion symmetry in sequences of mutamers in dynamic equilibrium in the crystal in domains at a mesoscopic scale comparable with the wavelength of light used. A control experiment was performed with a crystalline film of a similar tetrayne molecule, 1,4-bis­(3-((trimethylsilyl)­ethynyl)­bicyclo­[1.1.1]­pent-1-yl)­buta-1,3-diyne, whose bicyclopentane units can rotate but are achiral and produce no second-order optical response