Observation of the Strong Electronic Coupling in Near-Infrared-Absorbing Tetraferrocene aza-Dipyrromethene and aza-BODIPY with Direct Ferrocene-α- and Ferrocene-ß-Pyrrole Bonds: Toward Molecular Machinery with Four-Bit Information Storage Capacity.

The 1,3,7,9-tetraferrocenylazadipyrromethene (3) and the corresponding 1,3,5,7-tetraferrocene aza-BODIPY (4) were prepared via three and four synthetic steps, respectively, starting from ferrocenecarbaldehyde using the chalcone-type synthetic methodology. The novel tetra-iron compounds have ferrocene groups directly attached to both the α- and the ß-pyrrolic positions, and the shortest Fe-Fe distance determined by X-ray crystallography for 3 was found to be ∼6.98 Å. These new compounds were characterized by UV-vis, nuclear magnetic resonance, and high-resolution electrospray ionization mass spectrometry methods, while metal-metal couplings in these systems were probed by electro- and spectroelectrochemistry, chemical oxidations, and Mössbauer spectroscopy. Electrochemical data are suggestive of the well-separated stepwise oxidations of all four ferrocene groups in 3 and 4, while spectroelectrochemical and chemical oxidation experiments allowed for characterization of the mixed-valence forms in the target compounds. Intervalence charge-transfer band analyses indicate that the mixed-valence [3]+ and [4]+ complexes belong to the weakly coupled class II systems in the Robin-Day classification. This interpretation was further supported by Mössbauer spectroscopy in which two individual doublets for Fe(II) and Fe(III) centers were observed in room-temperature experiments for the mixed-valence [3]n+ and [4]n+ species (n = 1-3). The electronic structure, redox properties, and UV-vis spectra of new systems were correlated with Density Functional Theory (DFT) and time-dependent DFT calculations (TDDFT), which are suggestive of a ferrocene-centered highest occupied molecular orbital and chromophore-centered lowest unoccupied molecular orbital in 3 and 4 as well as predominant spin localization at the ferrocene fragment attached to the α-pyrrolic positions in [3]+ and [4]+.

Re(CO)3-Templated Formation of Aza(dibenzo)dipyrromethenes.

The Re(CO)3 unit was used to template the formation of aza(dibenzopyrro)methene (ADBM) in the presence of pyridine or N-methylimidazole. The products of these template reactions are six-coordinate complexes, with a facial arrangement of the carbonyls, a bidentate ADBM, and a sixth ligand (pyridine or N-methylimiadozle). Three types of ADBM ligands are produced from these reactions, depending on the degree of hydrolysis; bis(imine)-terminated, bis(oxo)-terminated, and mixed-imine/oxo chelates were formed.

Using Hydrazine to Link Ferrocene with Re(CO)3: A Modular Approach.

Acetyl ferrocene and diacetyl ferrocene both readily react with an excess of hydrazine to afford the corresponding hydrazone compounds. These compounds can then be linked to Re(CO)3 via a metal-mediated Schiff base reaction, resulting in a series of ferrocene-Re(CO)3 conjugates with different stoichiometries. Conjugates with 1:1, 1:2, and 2:1 ferrocene: Re(CO)3 ratios can be produced via this "modular" type synthesis approach. Several examples of these conjugates were structurally characterized, and their spectroscopic, electrochemical, and spectroelectrochemical behaviors were investigated. The electronic structures of these compounds were also probed using DFT and TDDFT calculations.

Unusually Strong Long-Distance Metal-Metal Coupling in Bis(ferrocene)-Containing BOPHY: An Introduction to Organometallic BOPHYs.

The first organometallic BOPHY (BOPHY=bis(difluoroboron)-1,2-bis{(pyrrol-2-yl)methylene}hydrazine) containing two ferrocene substituents was prepared through a Knoevenagel condensation between tetramethyl substituted BOPHY and ferrocene carboxaldehyde. An unprecedentedly strong long-range (≈17.2 Å) metal-metal coupling in this new complex was investigated using electrochemical, spectroelectrochemical, and chemical oxidation methods. Electrochemical data is indicative of a 200 mV separation between the first and the second ferrocene-centered oxidation processes. Formation of the mixed-valence states and appearance and disappearance of two NIR bands were observed during stepwise oxidation of the first organometallic BOPHY. The electronic structure and the nature of the excited states in this new chromophore were studied by DFT and TDDFT calculations.

Synthesis, redox properties, and electronic coupling in the diferrocene aza-dipyrromethene and azaBODIPY donor-acceptor dyad with direct ferrocene-α-pyrrole bond.

3,3'-Diferrocenylazadipyrromethene (3) and corresponding difluoroboryl (azaBODIPY) complex (4) were synthesized in several steps from ferrocenecarbaldehyde, following the well-explored chalcone-type synthetic approach. The novel diiron complexes, in which ferrocene groups are directly connected to the α-pyrrolic positions were characterized by a variety of spectroscopic techniques, electrochemistry, spectroelectrochemistry, and X-ray crystallography, while their electronic structure, redox properties, and UV-vis spectra were correlated with the density functional theory (DFT) and time-dependent DFT calculations.

2,2'-[2,4-Bis(naphthalen-1-yl)cyclo-butane-1,3-di-yl]bis-(1-methyl-pyridinium) bis-(4-chloro-benzene-sulfonate): thermal-induced [2 + 2] cyclo-addition reaction of a heterostilbene.

The asymmetric unit of the title salt, C36H32N2 (2+)·2C6H4ClO3S(-), consists of one anion and one half-cation, the other half being generated by inversion symmetry. The dihedral angle between the pyridinium ring and the napthalene ring system in the asymmetric unit is 42.86 (6)°. In the crystal, cations and anions are linked by weak C-H⋯O inter-actions into chains along [010]. Adjacent chains are further arranged in an anti-parallel manner into sheets parallel to the bc plane. π-π inter-actions are observed involving the cations, with centroid-centroid distances of 3.7664 (8) and 3.8553 (8) Å.

Aza-BODIPY-based logic gate chemosensors and their applications.

Dimethylaniline-substituted aza-BODIPY dyes (DA, DM, DP) were designed and synthesized aiming for ion detection. The Zn2+ recognition ability was found in all compounds and the binding mechanism was possibly via dimethylaniline sites linked to the aza-BODIPY core. Upon Zn2+ addition, the new absorption band and the color change occurred due to the altered charge transfer of the adducts. The custom-made colorimeter was successfully integrated into the dye's application, demonstrating a good linear relationship between resistance values and Zn2+ concentration. The chromophore test strips were fabricated and exhibited distinct color changes upon aqueous Zn2+ exposure. The compound DA also exhibits logical behavior with DA-Zn2+-Cu2+ system. In terms of environmental hazards, the compounds exhibited no adverse effect on Pseudomonas putida at the concentration level of 0.2 mg/mL. These findings indicated that all synthesized aza-BODIPYs might be suitable for chemosensor probes for Zn2+ detection with possibly low environmental risk.

The synthesis of biologically relevant conjugates of Re(CO)3 using pyridine-2-carboxyaldehyde.

The new pyridine-2-carboxaldehyde adduct, Re(CO)3(NC6H5C(O)H)Cl 1, and previously reported complex Re(CO)3(NC6H5C(O)H)Br 2 react with aniline derivatives sulfanilamide or 4-aminofluorescein in methanol giving Schiff base conjugates Re(CO)3(pyca-R)X (pyca = pyridinecarbaldehyde imine, X = Cl, Br), 3-6. Pre-isolation of compounds 1 and 2 provides a convenient method for preparing conjugate complexes in addition to the known methods of ligand synthesis and one-pot reactions. All new compounds were completely characterized, and compound 1 and the sulfanilamide derivatives 3 and 4 were structurally elucidated by X-ray crystallography.

(E)-2-[4-(Di-ethyl-amino)-styr-yl]-1-methyl-quinolinium 4-fluoro-benzene-sulfonate monohydrate.

In the title hydrated molecular salt, C22H25N2 (+)·C6H4FO3S(-)·H2O, the cation displays whole mol-ecule disorder over two sets of sites in a 0.780 (5):0.220 (5) ratio. The quinolinium ring system is essentially planar, with r.m.s. deviations of 0.0162 and 0.0381 Šfor the major and minor disorder components, respectively. The dihedral angles between the mean plane of the quinolinium ring system and the benzene ring are 5.1 (3) and 7.7 (11)°, respectively, for the major and minor components in the cation. In the crystal, cations, anions and water mol-ecules are linked into chains along [010] by O-H⋯O hydrogen bonds and are further connected into a three-dimensional network by weak C-H⋯O and C-H⋯F inter-actions. In addition, π-π inter-actions with centroid-centroid distances of 3.634 (3), 3.702 (5) and 3.838 (5) Šare observed.

2,2'-[2,4-Bis(naphthalen-1-yl)cyclo-butane-1,3-di-yl]bis-(1-methyl-pyridinium) diiodide: thermal-induced [2†+†2] cyclo-addition reaction of a heterostilbene.

The asymmetric unit of the title compound, C(36)H(32)N(2) (2+)·2I(-), consists of one half-mol-ecule of the cation and one I(-) anion. The cation is located on an inversion centre. The dihedral angle between the pyridinium ring and the naphthalene ring system in the asymmetric unit is 19.01 (14)°. In the crystal, the cations and the anions are linked by C-H⋯I inter-actions into a layer parallel to the bc plane. Intra- and inter-molecular π-π inter-actions with centroid-centroid distances of 3.533 (2)-3.807 (2) Šare also observed.

Colorimetric Cu2+ Detection of (1E,2E)-1,2-Bis((1H-pyrrol-2-yl)methylene)hydrazine Using a Custom-Built Colorimeter.

The compound (1E,2E)-1,2-bis((1H-pyrrol-2-yl)methylene)hydrazine (1) was investigated for its chemosensor application. The colorimetric response of 1 with various ions was investigated, and the selective optical change upon mixing with Cu2+ was found. The Cu2+ binding stoichiometry of 1 derived from Job's plot and the in silico study give us the tentative structural detail of the binding mode of 1 and Cu2+ being 1:1. The binding constant between 1 and Cu2+ from the Benesi-Hildebrand plot was 1.49 × 104 M-1. The limit of detection of 1 in Cu2+ detection was 0.64 µM (0.040 ppm), which is much lower than the WHO and US EPA maximum allowable Cu2+ level in drinking water (2 and 1.3 ppm, respectively). The custom-built colorimeter demonstrates a good linear relationship between Cu2+ concentration and electrical resistance (Ω) upon 1-Cu2+ ion binding.

2-(2-Hy-droxy-3-meth-oxy-phen-yl)-6H-perimidin-6-one.

The mol-ecule of the title perimidine derivative, C(18)H(12)N(2)O(3), is essentially planar, the dihedral angle between the benzene and perimidine rings being 3.25 (5)°. The hy-droxy and meth-oxy groups lie in the plane of the benzene ring to which they are bound [O-C-C-C = 179.96 (11)° and C-O-C-C = -177.96 (12)°]. An intra-molecular O-H⋯N inter-action generates an S(6) ring motif. In the crystal, mol-ecules are linked by pairs of C-H⋯O inter-actions into dimers, which generate S(16) ring motifs. These dimers are arranged into sheets parallel to the ac plane and further stacked down the b axis by π-π inter-actions, with centroid-centroid distances in the range 3.5066 (8)-3.7241 (7) Å.

2-[(E)-2-(4-Eth-oxy-phen-yl)ethen-yl]-1-methyl-pyridinium 4-chloro-benzene-sulfonate monohydrate.

In the title compound, C(16)H(18)NO(+)·C(6)H(4)ClO(3)S(-)·H(2)O, the cation exists in an E configuration with respect to the ethenyl bond and is slightly twisted with a dihedral angle of 9.85 (5)° between the pyridinium and the benzene rings. The anion is inclined to the cation with the dihedral angles between the benzene ring of the anion and the pyridinium and benzene rings of the cation of 78.33 (6) and 68.73 (6)°, respectively. In the crystal, the cations and anions are arranged alternately into head-to-head ribbons along the c axis, with the cationic ribbons stacked along the b axis. The crystal is consolidated by O-H⋯O hydrogen bonds, weak C-H⋯O and C-H⋯π inter-actions. π-π inter-actions with centroid-centroid distances of 3.6111 (7) and 3.6466 (7) Šare also observed.

(E)-2-[4-(Dimethyl-amino)-styr-yl]-1-methyl-pyridinium triiodide.

The asymmetric unit of the title compound, C(16)H(19)N(2) (+)·I(3) (-), contains a (E)-2-[4-(dimethyl-amino)-styr-yl)-1-methyl-pyrid-in-ium cation and half each of two triiodide anions. The complete triiodide anions are each generated by inversion symmetry. The planar cation has all of its eighteen non-H atoms situated on a mirror plane. In the crystal, the cations are stacked along the b axis by π-π inter-actions with a centroid-centroid distance of 3.5757 (13) Å. The triiodide anions are located between the cations. The crystal structure is further consolidated by short C⋯C [3.322 (9)-3.3952 (19) Å] contacts.

(E)-1-(4-Amino-phen-yl)-3-(pyridin-3-yl)prop-2-en-1-one.

The title chalcone derivative, C(14)H(12)N(2)O, consists of 4-amino-phenyl and pyridine rings bridged by a prop-2-en-1-one unit and exists in a trans configuration with respect to the C=C double bond. The mol-ecule is slightly twisted with a dihedral angle of 29.38 (7)° between the benzene and pyridine rings. The prop-2-en-1-one bridge is nearly planar with an r.m.s. deviation of 0.0384 (1) Šand makes dihedral angles of 15.40 (9) and 16.30 (9)°, respectively, with the benzene and pyridine rings. In the crystal, mol-ecules are linked by N-H⋯N and N-H⋯O hydrogen bonds into a layer parallel to the ab plane. A π-π inter-action with a centroid-centroid distance of 3.6946 (10) Šis also observed.

(E)-2-[4-(Diethyl-amino)-styr-yl]-1-methyl-pyridinium benzene-sulfonate mono-hydrate.

The asymmetric unit of the title compound, C(18)H(23)N(2) (+)·C(6)H(5)O(3)S(-)·H(2)O, comprises a 2-[4-(diethyl-amino)-styr-yl]-1-methyl-pyridinium cation, a benzene-sulfonate anion and a solvent water mol-ecule. One ethyl substituent of the diethyl-amino group of the cation is disordered over two positions in a 0.73789 (9):0.26211 (9) ratio. The cation exists in the E configuration with respect to the C=C bond and the π-conjugated system is essentially planar with a dihedral angle of 0.82 (10)° between the pyridinium and benzene rings. The cation and anion are almost orthogonal with a dihedral angle of 86.71 (10)° between the π-conjugated system of the cation and benzene ring of the anion. In the crystal, mol-ecules are arranged into chains along [001] and adjacent chains are linked by weak C-H⋯O inter-actions. The crystal is further stablilized by O-H⋯O hydrogen bonds and weak C-H⋯π inter-actions.

(E)-1-(2-Hy-droxy-phen-yl)-3-(2,4,5-trimeth-oxy-phen-yl)prop-2-en-1-one.

In the title chalcone derivative, C(18)H(18)O(5), the dihedral angle between the hy-droxy-substituted benzene ring and the trimeth-oxy-substituted benzene ring is 16.3 (1)°. The three meth-oxy groups are essentially coplanar with the benzene ring to which they are attached, with an r.m.s. deviation of 0.0208 Å. An intra-molecular O-H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, weak C-H⋯O inter-actions link mol-ecules into helical chains along the b axis. These chains are connected into sheets parallel to the bc plane by further weak C-H⋯O inter-actions.

(E)-2-[4-(Diethyl-amino)-styr-yl]-1-methyl-pyridinium 4-chloro-benzene-sulfonate monohydrate.

In the title hydrated mol-ecular salt, C(18)H(23)N(2) (+)·C(6)H(4)ClO(3)S(-)·H(2)O, which shows moderate biological activity against methicillin-resistant Staphylococcus aureus (MRSA), one ethyl group of the 2-[4-(diethyl-amino)-styr-yl]-1-methyl-pyridinium cation is disordered over two orientations in a 0.604 (13):0.396 (13) ratio. The main part of the cation is nearly planar with a dihedral angle of 4.50 (10)° between the pyridinium and benzene rings. In the crystal, the components are linked by O-H⋯O hydrogen bonds and C-H⋯O weak inter-actions. Aromatic π-π stacking inter-actions with centroid-centroid separations of 3.7363 (12) and 3.7490 (13) Šalso occur.

(1E,1'E)-4,4'-[1,1'-(Hydrazine-1,2-diyl-idene)bis-(ethan-1-yl-1-yl-idene)]diphenol dihydrate.

The asymmetric unit of the title compound, C(16)H(16)N(2)O(2)·2H(2)O, contains one half-mol-ecule of diphenol and one water mol-ecule. The complete diphenol mol-ecule is generated by a crystallographic inversion centre. In the mol-ecule, the central C(meth-yl)-C=N-N=C-C(meth-yl) plane makes a dihedral angle of 8.88 (6)° with its adjacent benzene ring. In the crystal, the components are linked by O-H⋯N and O-H⋯O hydrogen bonds into a three-dimensional network. The crystal structure is further stabilized by a weak C-H⋯π inter-action.

Redetermination of (E)-3-(anthracen-9-yl)-1-(2-hy-droxy-phen-yl)prop-2-en-1-one.

The redetermined structure of title chalcone derivative, C(23)H(16)O(2), corrects errors in the title, scheme and synthesis in the previous report of the same structure [Jasinski et al. (2011 ▶). Acta Cryst. E67, o795]. There are two independent mol-ecules in the asymmetric unit with slight differences in bond lengths and angles. The dihedral angle between the benzene ring and the anthracene ring system is 73.30 (4)° in one mol-ecule and 73.18 (4)° in the other. Both mol-ecules feature an intra-molecular O-H⋯O hydrogen bond, which generates an S(6) ring. In the crystal, mol-ecules are arranged into sheets lying parallel to the ac plane and further stacked along the b axis by π-π inter-actions with centroid-centroid distances in the range 3.6421 (6)-3.7607 (6) Å. The crystal structure is further stabilized by C-H⋯π inter-actions. There are also C⋯O [3.2159 (15) Å] short contacts.