Herein,
tetrabromoterepthalic acid (TBTA) is used as the potential co-crystal
former with various organic base molecules containing free nitrogen
atoms. The crystal structure of TBTA (compound 1) has
been determined from powder X-ray diffraction (PXRD) data. In a systematic
way, we have synthesized hydrated-TBTA (compound 2),
two salts of TBTA [TBTA2––4,4′-bipy2+ (compound 3), 4,4′-bipy = 4,4′-bipyridine,
and TBTA2––(3-AP+)2 (compound 4), 3-AP = 3-aminopyridine] and two co-crystals
of TBTA [TBTA–DPTZ (compound 5), DPTZ = 3,6-di(pyridyl-2-yl)-1,2,4,5-tetrazine,
and TBTA–(3-IP)2 (compound 6), 3-IP
= 3-iodopyridine]. All of the compounds were characterized by structural,
spectral, and thermal studies. Supramolecular structural analysis
reveals that 1 forms a 2D supramolecular sheet structure
by means of O–H···Br hydrogen bonding interactions
and hydrated-2 forms a 3D supramolecular structure through
water mediated hydrogen bonding interactions and π···
interactions. The O–H···N/O¯···H–N+ hydrogen bonding interactions between acid and base molecules
give rise to 1D supramolecular chain structure in 3 and
supramolecular trimers in 4, 5, and 6. Because of presence of charge assisted O¯···H–N+ hydrogen bonds between acid–base
molecules, 3 and 4 form hydrogen bonds with
solvent water molecules, and also both 3 and 4 form 3D supramolecular structures using both hydrogen bonding and
π··· interactions. In co-crystal 5, solvent water molecules participate in crystallization in contrast
to 6, and it has been observed that 5 forms
3D supramolecular structure, while 6 forms 2D supramolecular
structure using both hydrogen bonding and π···
interactions. An investigation of intermolecular closed contacts has
been carried out by Hirshfeld surface analysis, and associated 2D
fingerprint plots reveal the similarities and differences of TBTA
molecules in these six crystal structures. Photoluminescence spectra
of all the compounds have been studied, and they reveal that with
change of polarity around TBTA luminescent intensity of the compounds
has been modified. I–V measurement
indicates that 3 shows semiconducting behavior, and the
ITO/3/Al sandwich structure acts as a Schottky barrier
diode. The device exhibits an excellent rectification ratio (19 at
±1 V) with an ideality factor of 2.96. The semiconducting behavior
of 3 is attributed to the formation charge assisted hydrogen
bonding interactions between acid and base molecules.
