The Aminoff prize is awarded in the name of Professor Gregori Aminoff (1883-1947), a descendent of a Russian officer who joined the Swedish army in 1612. Aminoff had two quite different careers-one as an artist and the other as a scientist. In his scientific career, Aminoff was a pioneer in the application of both x-ray diffraction and electron diffraction. His interest was the investigation of the crystal structures of a large number of minerals, and in particular those from Langban in Varmland, Sweden. The Aminoff prize, which has been awarded since 1979, rewards outstanding work in crystallography to both Swedish and foreign researchers. Some preference should be shown for work evincing elegance in the approach to the problem.

Potential energy surfaces for a series of intermolecular CH center dot center dot center dot O hydrogen bonds have been calculated in order to determine the Quantum Mechanical Reaction Coordinates (QMRCs). The results have shown that one QMRC curve is common for strong C-H center dot center dot center dot O hydrogen bonds, and another for very weak interactions. For intermediate hydrogen bonds the shape of the potential energy curve depends on the particular type of the C-H center dot center dot center dot O bond, which is related to the proton donor ability and geometry of the hydrogen bridge.

The influence of temperature on the proton location in hydrogen bonds has been systematically studied by neutron diffraction in only a few crystal structures. Two of these are the 1: 1 complex of urea - phosphoric acid with an OHO hydrogen bond and 4-methylpyridine-pentachlorophenol with an OHN hydrogen bond. Based on these earlier determined crystal structures the potential energy surface (PES) at different temperatures has now been determined by DFT calculations at the B3LYP/6-31++G** level of theory using the Gaussian03 system. In general PES is practically unchanged as the proton moves from the donor to the acceptor. This is not surprising as the crystal structure does not undergo significant changes as the proton successively moves along the hydrogen bond. For both complexes PES is characterized by only one minimum, which is not located at the centre where the distances of the proton to the bridge atoms are the same. The experimental proton positions are located close to the calculated energy minima; the slight deviations are probably an effect of the crystalline environment which has not been taken into account in the calculations.

The potential energy curves for proton motion in NHN+ hydrogen bonds have been calculated to investigate whether different methods of evaluation give different results: for linear H bonds most curves calculated along the NH direction are, as expected, identical with those along NN; for intramolecular H bonds it is very important to take into account the non-linearity and the potential energy curve calculated along the NH direction can be very far from the curve correctly describing the proton transfer. Other factors which influence the proton-transfer process are steric hindrance and presence of anions which modify the proton motion. In the analysis of the proton transfer process it is very important to take changes in the structure of the rest of the molecule into account, which is connected with exchange of energy with the surroundings. Comparison of adiabatic and non-adiabatic curves shows that they are significantly different for very bent hydrogen bonds and for hydrogen bonds with steric constraints for which the proton transfer process must be accompanied with relaxation of the whole molecule. Comparison of the potential-energy curves for compounds with very short H bonds emphasizes that the term strong H bond needs to be qualified. For intermolecular H bonds shortening of the bond is connected with linearization. But for intramolecular H bonds the NN distance cannot be used as the only measure of H bond strength.

The quantum-mechanically derived reaction coordinates (QMRC) for the proton transfer in (N—H—N)⁺ hydrogen bonds have been derived from ab initio calculations of potential-energy surfaces. A comparison is made between the QMRC and the corresponding bond-order reaction coordinates (BORC) derived by applying the Pauling bond-order concept together with the principle of conservation of bond order. We find virtually perfect agreement between the QMRC and the BORC for intermolecular (N—H—N)⁺ hydrogen bonds. In contrast, for intramolecular (N—H—N)⁺ hydrogen bonds, the donor and acceptor parts of the molecule impose strong constraints on the N—N distance and the QMRC does not follow the BORC relation in the whole range. The X-ray determined hydrogen positions are not located exactly at the theoretically calculated potential-energy minima, but instead at the point where the QMRC and the BORC coincide with each other. On the other hand, the optimized hydrogen positions, with other atoms in the cation fixed as in the crystal structure, are closer to these energy minima. Inclusion of the closest neighbours in the theoretical calculations has a rather small effect on the optimized hydrogen positions. [Part I: Olovsson (2006). Z. Phys. Chem.220, 797–810.]

The 'quantum-mechanically derived reaction coordinates' (QMRC) for the proton transfer in hydrogen bonds involving fluorine, oxygen and chlorine have been derived from earlier ab initio calculations of potential energy surfaces. A comparison is made between QMRC and the corresponding reaction coordinates (BORC) derived by applying the Pauling bond order concept together with the principle of conservation of bond order. Theoretical calculation have shown that sum of the bond orders remains close to constant along the reaction coordinate in agreement with the Pauling postulate. The BORC correlation curves agree very well with theoretical results. The results indicate that the BORC curve gives a good representation of the reaction coordinates (ptoton transfer path) for any X-H---Y aggregate.

The paper discusses some aspects of the electron lone-pairs in H-bonded structures: their role in determining the short-range structure and the effect of the environment on the electron density. In the water molecule the entire non blonded region apperars to be equally accessible for hydrogen bonding and the details of the hydrogen-bond arrangement are mainly determined by simple geometrical and topological requirements.

Many examples may be taken to illustrate that it is important to take the whole electron and nuclear distribution into account when discussing the relative arrangement of interacting molecules. The resulting structure of one particular compound is determined by the net balance of many intermolecular interactions and not only by the hydrogen bonding, even if the resulting structure is consistent with hydrogen-bond directionality. From structural data it can be concluded that immediate accptor of a hydrogen bond is some negative charge accumulation, such as in a lone-pair region, but not specifically any individual lone pairs in the traditional, atomic sense.

Crystal structure of Rb3D(SeO4)2 has been investigated at 25 K (below the transition temperature Tc = 95.4 K) by single-crystal neutron diffraction. Accompanying the transition, the SeC04 groups, which are all equivalent in the phase above the transition (space group A2/a), split into eight nonequivalent groups in a superlattice (a X 2b X 2c, space group A2) in the low-temperature phase. Based on the D atom positions obtained, each of the SeO4 groups was identified to be in the state closer to a HSeO4- ion or to a SeO4²- ion and the dipole arrangement of SeO4-D-SeO4 dimer was revealed. This dipole arrangement has 'ferri' structure along the polar b-axis, but 'antiferro' structure in the plane perpendicular to the b-axis. These results are consistent with the characteristics found in the earlier dielectric measurements.