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A method was developed to prepare 2-acylaminobenzo[1,3]tellurazoles from bis(2-aminophenyl) ditellurides and acylisothiocyanates in good yield following a simple two-step, one pot procedure. It consists of the formation of acylthioureas, followed by reductive cyclization. This method relies on readily accessible precursors and avoids the use of reagents that are highly toxic or sensitive to air or moisture. Three representative products were characterized by X-ray crystallography to probe their tendency to undergo intermolecular chalcogen bonding. 4,6-Dimethyl-2-acetylaminobenzo[1,3]tellurazole lacked such bonding while 5-methyl-2-acetylaminobenzo[1,3] tellurazole showed Te…N secondary bonding and 2-acetamidobenzo[1,3]tellurazole formed a supramolecular tetramer as a result of Te…Ocarbonyl bonding interactions. A computational non-covalent interaction analysis of this tetramer was performed, which indicates that it is more stable by ~58 kcal mol-1 than the monomer would be. 

The title compound, C₈H₇Cl₂NO₂, crystallizes in the triclinic space groupP1with three molecules in the asymmetric unit. Two of them are essentially planar, with mean deviations of 13 non-hydrogen atoms of 0.029 and 0.030 Å, and differ only in the conformation of the O—H hydrogen atom. The third molecule is quite nonplanar, with the CCNO acetamide plane forming a dihedral angle of 67.56 (5)° with the remainder of the molecule. In the extended structure, the two almost planar molecules form antiparallel hydrogen-bonded chains through N—H...O interactions of the acetamide substituents. The N—H group of the nonplanar molecule donates a bifurcated hydrogen bond to the O—H group and a Cl substituent of one of the planar molecules. The O—H groups of all molecules form intermolecular hydrogen bonds to other O—H groups or carbonyl O atoms. Together, the hydrogen bonds generate a three-dimensional network. 

A series of 1,3,5,7-tetraphenyl-aza-BODIPY dyes functionalized with electron-donating or withdrawing groups at the para-positions of the phenyl rings on either the 1,7- or 3,5-positions were synthesized and characterized. The electron-donating group selected was –NH2, while the electron-withdrawing groups spanned a range of strengths, from strong (-NO2) to moderate (-NH3+) and mild (-Ndouble bondCdouble bondS). The structural modifications were strategically implemented to investigate their impact on the dyes photophysical properties. Spectroscopic studies revealed that these dyes exhibit intense absorption and emission in the near-infrared (NIR) region (678–855 nm). The photophysical properties, including molar absorptivity, fluorescence quantum yield, and Stokes shift were found to depend significantly on both the electronic nature (donating/withdrawing) and positioning (1,7- vs. 3,5-) of the substituents. Complementary computational studies provided insights into the electronic structures and excited-state dynamics, corroborating experimental observations. Time-dependent density functional theory (TD-DFT) calculations revealed that the electron density distribution and the frontier orbitals’ energies and shapes were significantly influenced by the electronic effects of the substituent groups. This study underscores the tunability of aza-BODIPY dyes through rational molecular design, enabling precise control over their optical properties for tailored NIR applications. 

In the title compound, C₁₀H₁₀ClNO₃, the dihedral angles between the chlorobenzene ring and the acetamide and acetate planes are 40.70 (8) and 88.07 (8)°, respectively; the acetamide and acetate planes make a dihedral angle of 51.39 (9)°. In the extended structure, the molecules are linked by N—H...O hydrogen bonds involving the acetamide group, formingC(4) chains propagating along the [010] direction. 

In the title compound, C₈H₈ClNO₂, the acetamide substituent is twisted out of the phenyl plane, forming a dihedral angle of 58.61 (7)°. In the extended structure, each molecule donates two hydrogen bonds [N—H...O(carbonyl) and O—H...O(carbonyl)] and thus also accepts two such hydrogen bonds. The chlorine atom is not involved in the hydrogen bonding. 

In the title compound, C10H12N2O4, the four substituents lie out of the phenyl plane by varying degrees. The methyl C atom lies 0.019 (3) A ˚ out of plane, while the methoxy O and C atoms lie 0.067 (2) and 0.042 (3) A ˚ out of plane, respectively, with the C—C—O—C torsion angle being 3.3 (2). The plane of the nitro group is twisted out of the phenyl plane, forming a dihedral angle of 12.03 (9) with it. The acetamide substituent is twisted considerably more out of the phenyl plane, forming a dihedral angle of 47.24 (6) with it. In the extended structure, the acetamide NH group donates a hydrogen bond to an acetamide carbonyl O atom, thereby forming chains propagating in the [010] direction. 

The modular synthesis of a fluorene-based nanohoop containing six strained alkynes is described herein. We demonstrate its scalability using alkyne metathesis as the macrocyclization method and its reactivity with azides... 

The title compound, C₆H₇ClNO⁺·Cl⁻, crystallizes in orthorhombic space groupPnmawith both cations and anions lying on a mirror plane in the crystal. The C—Cl distance is 1.7289 (6) Å, the C—N distance is 1.4590 (8) Å, and the C—O distance is 1.3617 (8) Å. Parallel molecules form stacks with interplanar spacing 3.1473 (2) Å, but slipped by 1.97 Å. The NH₃⁺substituent donates three intermolecular hydrogen bonds to chloride ions having N...Cl distances in the range 3.1514 (6)–3.3019 (2) Å, and the OH group donates an intermolecular hydrogen bond to chloride with O...Cl distance 3.0671 (6) Å. The chloro substituent and OH group do not accept hydrogen bonds from NH or OH.