The magnetic and electronic properties of metal phthalocyanines (MPc) and fluorinated metal phthalocyanines (F 16 MPc) are studied by means of spin density functional theory (SDFT). Several metals (M) such as Ca, all first d-row transition metals and Ag are investigated. By considering different open shell transition metals it is possible to tune the electronic properties of MPc, in particular the electronic molecular gap and total magnetic moment. Besides assigning the structural and electronic properties of MPc and F 16 MPc, the vibrational modes analysis of the ScPc-ZnPc series have been studied and correlated to experimental measurements when available.

The hydrogen-bonding interaction energies have been computed for a series of five homo-and heterodimers formed between boronic acids, carboxylic acids, and carboxylate anions using ab initio methods at the MP2/6-31G(d,p) level. The results show that the stability of these systems decreases in the following direction: RB(OH) 2 ‚‚‚ -OOCR > RCOOH‚‚‚ -OOCR >> RCOOH‚‚‚HOOCR > RB(OH) 2 ‚‚‚HOOCR > RB(OH) 2 ‚‚‚(HO) 2 BR; (R ) Me, Ph). Five crystals containing boronic acids and carboxylate anions have been prepared and characterized both in solution and the solid-state using spectroscopic as well as X-ray crystallographic methods. The interaction energies of the RB(OH) 2 ‚‚‚ -OOCR heterodimeric motifs are more than double those of the homodimeric RCOOH‚‚‚HOOCR and RB(OH) 2 ‚‚‚(HO) 2 BR motifs. This was proved by the fact that these anionic systems were stable in solution, even in polar solvents such as DMSO. The solid-state analysis provided detailed geometric data for one of these systems. The predicted interaction energies for the RB(OH) 2 ‚‚‚HOOCR heterodimers are intermediate between the energies for the corresponding RCOOH‚‚‚HOOCR and RB(OH) 2 ‚‚‚(HO) 2 BR homodimers; nevertheless, crystals containing such a system could not be obtained. Despite of this, these experiments provided two new systems containing hydrogen-bonding interactions between neutral carboxylic and boronic acids.

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Nine tetraalkylammonium salts, with R 5 Me, Et, n Pr and n Bu, of four different carboxylic acids, namely isophthalic acid, 5-nitroisophthalic acid, trimesic acid and pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid), have been prepared and their supramolecular structures analyzed by X-ray crystallography. The [RCOOH· · ·HOOCR] homodimeric motif characteristic for carboxylic acids has not been detected, but instead, in all compounds a [RCOOH· · ·OOCR] 2 unit was present. The hydrogen-bonding geometries and interaction energies of the different discrete and water-expanded hydrogen-bonding patterns formed between the carboxyl and the carboxylate group have been analyzed systematically by theoretical calculations at the MP2/6-31G(d,p) level of theory.Carboxylates are promising candidates for crystal engineering and [OZH· · ·O] 2 interactions play an important role for the structural organization and chemistry of biomolecules.