The Swedish chair of Chemistry was established in 1908 as the second oldest chair of chemistry in Finland. The holder may represent any branch of chemistry but will lecture in Swedish, the second domestic lang uage of Finland. Most students in this subdepartment belong to the Swedish-speaking min ority of the country; the others share the current scientific interests.

The somewhat unusual mission of the subdepartment has permitted it t o pioneer both wood and lignin chemistry and, to an extent, theoretical chemistry in Fi nland, while safe-guarding the constitutional linguistic rights of the minority. The su bdepartment offers both introductory courses and higher, M.Sc. and postgraduate courses . After almost 32 years at Et. Hesperiankatu 4 in downtown Helsinki, the Laboratory mov ed to the Kumpula campus in May 1995.

Teaching staff

Pekka Pyykkö, Ph.D., Professor (on leave Aug. 1, 1995 - July 31 , 2000), Head of the Laboratory

Michaela Ekholm, Lic.Phil., Teaching Assistant

Henrik Konschin, Ph.D., Doc. (Kuopio), Senior Teaching Assistant

Carola Olkkonen, Lic.Phil., Acting Teaching Assistant

Dage Sundholm, Ph.D., Doc., Acting Professor

Bertel Westermark, Ph.D., Lecturer

Research staff

Igor Goidenko, Ph.D., Research Visitor (Russia) (Jan. 1 - Feb. 13, Apr. 28 - June 29)

Leonti Labzowsky, Professor (Feb. 1 - Mar. 13)

Pekka Pyykkö, Research Professor (Academy of Finland, Aug. 1, 1 995 -)

Nino Runeberg, Ph.D., Research Scientist (Academy of Finland)

Michal Straka, M.Sc., Graduate Student (Czech Republic) (May 15 - Ju ly 15, Oct. 1-)

Toomas Tamm, Ph.D., Research Visitor (Estonia) (- Aug. 31)

Maria Tokman, Ph.D., Research Visitor (Russia) (- Oct. 31)

Henrik Tylli, Ph.D., Doc., Amanuensis

Administrative and technical staff

Jonas Juselius, System Manager

Bjarne Lindström, Eng., Laboratory Assistant

Susanne Lundberg, Dipl. Corr., Secretary

In order to develop a full working vocabulary in the students' mothe r tongue, parallel lecture courses in Swedish are being offered in Analytical, Organic and Physical Chemistry, in addition to the introductory, General Chemistry course. The corresponding laboratory exercises are offered in other subjects, apart from Physical C hemistry. This entire program roughly covers the first three years of study.

Higher courses were given in Theoretical Chemistry. This includes th e Winter School in Theoretical Chemistry. Advanced laboratory courses including researc h projects for the M.Sc. degree were given in Organic Chemistry.

Courses which are taught in Swedish in the Laboratory for Instructio n in Swedish:

Cum laude (medium) level (47 credits)

Lecture courses:

General Chemistry (4 credits)

Analytical Chemistry (3 credits)

Physical Chemistry

Thermodynamics (3 credits)

Atomic and Molecular Structure (3 credits)

Dynamics (2 credits)

Organic Chemistry I (2 credits)

Organic Chemistry II (4 credits)

Laboratory courses:

Introductory Inorganic Chemistry Laboratory (4 credits)

Intermediate Inorganic Chemistry Laboratory (3 credits)

Introductory Organic Chemistry Laboratory (4 credits)

Intermediate Organic Chemistry Laboratory (3 credits)

Laudatur (advanced) level:

Organic Chemistry:

Advanced Organic Chemistry Laboratory (3 credits)

Introduction to Degree Thesis in Organic Chemistry (5 credits)

Research Project for the M.Sc. Degree in Organic Chemistry (14 credi ts)

Degree Thesis for Organic Chemistry majors (15 credits)

Final Examination for Organic Chemistry majors (6 credits)

Conservation of Orbital Symmetry (1 credit)

Organic Chemistry of Natural Products (1 credit)

Topics in Preparative Organic Chemistry (2 credits)

Physical Chemistry:

Research Project for the M.Sc. Degree in Physical Chemistry (14 cred its)

Degree Thesis for Physical Chemistry majors (15 credits)

Quantum Chemistry (5 credits)

Relativistic Quantum Chemistry (5 credits)

Ab Initio Methods in Quantum Chemistry (3 credits)

Pulp and paper chemistry

The studies on the chemistry of pulp and paper were carried out in c ollaboration with scientists at The Finnish Pulp and Paper Research Institute (KCL), Pa per Science Centre.

The research aiming at a deeper understanding of the mechanism of di scolouration of pulp and paper is continuing. The influence of light and heat on variou s pulp components and the participation of carbohydrate-derived chromophores have been studied using different spectroscopic techniques. Holocelluloses isolated from kraft pu lp and from kraft pulp bleached with oxygen, ozone or hydrogen peroxide have been irrad iated selectively at 350 nm for various times and the changes have been monitored with fluorescence spectroscopy (Tylli, H., Forsskåhl, I., Olkkonen, C. a nd Hortling, B.)(18). The kinetics of the emission characteristics during monochromatic irradiation was also studied with emission spectroscopy.

To study the response of hemicellulose to artificial aging different xylan fractions from birch were treated with heat and light. The sensitivity of the sa mples to the various treatment was studied using UV-VIS reflectance, FTIR and fluoresc ence spectroscopy and the magnitude of the changes was assessed (Forsskåhl, I., T ylli, H., Hortling, B. and Olkkonen, C)(16). It is evident that heat and light a ctivate partly different reaction pathways in the aging process in pulps.

Accelerated thermal aging of a number of model compounds of wood ext ractives, both unsaturated fatty acids and resin acids in the neat state were performed to study the contribution of extractives to pulp aging (Forsskåhl, I., Olkkonen, C. and Tylli, H.)(17). The oxidation and degradation was studied with chromatographic and spectroscopic techniques. Large differences in reactivity was found between the var ious model compounds. All fatty acids degraded thermally, but some of the resin acids w ere rather stable.

Large amplitude modes play an important role in the energy transfer in molecules. A low-frequency Raman spectroscopic study of 1,3-dimethoxybenzene and its methyldeuterated analogue has been performed and the methyl torsional and low-frequenc y ring modes have been identified (Tylli, H.)(19).

Molecular modelling and ab initio structure calculations

Molecular modelling and quantum chemical calculations have been carr ied out on fairly large molecules of particular interest in various biosystems. The col laboration with drug designing pharmacologists at the University of Kuopio continues. In this context host-guest complexes are studied. The hosts are modelled from cyclodex trins and the guests are different pilocarpine prodrug molecules or other drug derivati ves.

The properties and structures of certain esterases are being investi gated. Acetylcholinesterase and butyrylcholinesterase and their various inhibitors and substrates have been modelled using both quantum chemical and molecular mechanics metho ds. A new homology model of butyrylcholinesterase built on the basis of acetylcholin esterase has been brought forward. (M. Ekholm & H. Konschin, J. Mol. Struct. Theoch em, 1998, in press).

Model systems characterizing substrate-enzyme interactions and recep tor-ligand interactions are of continuing interest. Theoretical calculations of sugar-b orate complexes have been performed to investigate structural details and to aid in the interpretation of the NMR-spectra of the complexes. Chlorophyllic model systems have b een studied quantum chemically using various levels of accuracy. The molecular structur e of six isomers and eight transition states of bonellin dimethylester were optimized a t density-functional level. The transition barriers for the inner hydrogen migration we re determined at second-order Møller-Plesset level. The nuclear magnetic shieldi ngs were calculated at Hartree-Fock level for each isomer and compared to experimental NMR data. (Sundholm, D., Konschin, H. and Häser, M., Chem. Eur. J., in press).

The molecular structure of chlorophyll a including the phytyl chain was optimized at density-functional level. Its UV/VIS spectrum was obtained at density -functional level using the time-dependent perturbation approach (TD-DFT). The calculat work-stuff line 100/302 32% ed and experimental spectra agree well. In the visible region, two new excited states w ith very weak line strengths were found. The calculations showed that the Gouterman <92>s generally accepted four-orbital model does not correctly describe the excitation spectrum of chlorophyll a (Sundholm, D., Chem. Phys. Lett., in press). The electronic spectra of porphyrins have also been studied at TD-DFT level. The obtained spectra are in a remarkable agreement with measured spectra (Sundholm, D., presented at the Canadi an Conference on Theoretical Chemistry, Vancouver).

Numerical quantum chemistry and determination of nuclear quadrupole moments

Analytic perturbation equations for the extended Koopmans<92> theore m have been derived. Ionization potentials obtained as energy differences and using the extended Koopmans<92> theorem expression, respectively, have been studied by analytic perturbation theory through 12<92>th order. A comparison of the expansions shows that t he extended Koopmans<92> theorem for the lowest ionization potential is exact for each order in the perturbation expansion (Olsen, J. and Sundholm, D)(5).

The atomic quadrupole moment and the electric field gradient at the nucleus of Ar⁺ were studied using our atomic MCHF program. The calcula ted atomic quadrupole is -0.5280 a.u. which is 1.4 % larger than the recently measured value (Sundholm, D., Phys. Rev. A, accepted).

The nuclear quadrupole moment of gallium was determined using atomi c data in ref. (Tokman, M., Sundholm, D. and Pyykkö, P.)(15).

A determination of Q(Al) using both molecular data on AlF and AlCl and atomic data on Al was submitted in 1998 (Kellö, V., Sadlej, A., Pyykkö, P., Sundholm, D., Tokman, M.). It was the first result of the COST Action D9 WG 9 <91> PAMALOF<92>.

Closed-shell attractions and other intermolecular forces

The van der Waals properties of radon were calculated for the first time in ref. (Runeberg, N. and Pyykkö, P.)(10) following a request from ex perimentalists.

The studies on the "aurophilic" Au(I)...Au(I) attraction w ere continued to doubly bridged, ring systems (Pyykkö, P. and Mendizabal, F.)(8) a nd to the centred X(AuL)_n^m+ (L=PR₃) systems (Pyykk&oum l;, P. and Tamm, T.)(9). They show unusual chemical properties, such as five- and six-c oordination for carbon. Another striking example is the giant proton affinity of about 1200 kJ/mol, calculated in (Pyykkö, P. and Tamm, T.)(9) for the experimentally k nown C(AuL)₄. The protonated species [H C(AuL)₄]⁺ is pyramidal, not tetrahedral (see Fig. 1) and experimentally astonishingly stable.

The same phenomenon in solid AgCl and AuCl was analyzed in collabor ation with University of Stuttgart in ref. (Doll, K., Pyykkö, P. and Stoll, H.)(3

During the year two Ph.D. students from Technische Universität München (TUM) visited the laboratory within the DAAD-supported exchange. One (M.A. Schmidt) got his Ph.D. at TUM.

Ab initio structure calculations at second-order Møller-Pless et level were carried out for p-chlorobenzoic acid dimers. The parallel van der Waals c omplex was found to have about 50% overlap of the benzene rings. The experimentally fou nd umbrella structure with the chlorines located above the benzene ring was found to be somewhat higher in energy and not a local minimum (Sundholm, D., Sundberg, M.R. and Ug gla, R.)(13).

During N. Runeberg<92>s post doctoral stay at Prof. H.-J. Werners gr oup (Theoretical Chemistry, University of Stuttgart), the theory for computing analytic al energy gradients for second-order multireference perturbation theory (CASPT2) was de rived. The general theory is valid for arbitrary MCSCF reference functions, including state-averaged references. This will make geometry optimization of larger molecules, ei ther in their ground or excited states, feasible at CASPT2 level. The actual implementa tion of the theory within the MOLPRO program package is advancing, and the theory, toge ther with the first calculated results are soon to be published.

The host group<92>s recent advances in local correlation methods ini tiated also another project, in which local electron-correlation methods were used in o rder to study the nature of the <91>aurophilic<92> attraction. Besides the well known d ispersion contribution, an additional important contribution arising from ionic excitat ions was found (Runeberg, N., Schütz, M., Werner, H.-J., J. Chem. Phys., accepted)

Beryllium Chemistry

The element beryllium was discovered by Vauquelin in 1798 and had he nce a bicentenary in 1998. It is amphoteric. Its behaviour in acidic solutions was unde rstood early on, but the species in basic solutions had not been characterized although Be(OH)₄^2- was commonly suggested. The paper (Schmidbaur, H. Schm idt, M., Schier, A., Riede, J., Tamm, T. and Pyykkö, P.)(11), combining syntheses and crystallography from Munich and calculations from Helsinki reports its actual stru cture, the adamantane-like [ Be₄(OH)_10] ^2-. The calculated and experimental structures agree well. (Fig. 2)

New chemical species

The first molecules with chemical bonds between noble metals and nob le gases were predicted in 1995 by P. Pyykkö. Three such systems, AuXe⁺ , XeAuXe⁺, and XeAu(C₆F₆)⁺ were observed m ass-spectroscopically in ref. (Schröder, D., Schwarz, H., Hru<9A>ák, J. and Pyykkö, P.)(12). Improved calculations on AuXe⁺ give a dissociation en ergy (D₀) of 126 kJ/mol for it, corresponding to an honest covalent bond. T he knowledge of this absolute value helps to fix the scale of Au⁺ affinities for the series of ligands

Xe<C₆F₆<H₂O<CO<H_{2< /SUB>S<CH3CN» C2H4» NH3 » CH3NC<CH3SCH3<PH3.}

The isoelectronic neutral systems PdXe and PtXe were also found to h ave fairly strong covalent bonds (Burda, J.V., Runeberg, N. and Pyykkö, P.)(2). T he first, and possibly the last triple bond to gold was predicted to exist in the so f ar unknown AuC⁺ (Barysz, M. and Pyykkö; P., Pyykkö, P. and Tamm, T.)(1, 7).

Ab initio calculations of magnetic properties of molecules

A simple interpretation for the "heavy-atom chemical shift" was prop osed in ref. (Kaupp, M., Malkina, O.L., Malkin, V.G. and Pyykkö, P.)(4). Fo r instance, the ¹³C and ¹H shifts in iodobenzene we re neatly interpreted. The work was done using density-functional methods in collaborat ion with MPI für Festkörperforschung in Stuttgart and University of Bratis lava.

A new computational method to determine the degree of aromaticity fr om ab initio wave functions has been developed (Jusélius, J. and Sundholm, D., presented at the International Conference on Quantum Chemical Calculations of NMR and E PR Parameters, Bratislava, submitted). The method has been applied to typical aromatic molecules such as benzene, thiophene, pyrrole and porphin. The calculations show that pyrrole and porphin are more aromatic than both benzene and thiophene.

Is quantum electrodynamics chemically relevant?

In addition to quantum mechanics and relativity, quantum electrodyna mics (QED) had a potential of influencing chemistry. Although the Lamb shift is more th an 50 years old, no estimates were available for the QED contribution to the valence e lectrons of heavy elements until our paper (Pyykkö, P., Tokman, M. and Labzowsky, L.N.)(6) for the alkali and coinage metals.

The effect turned out to be small but not negligible. For instance, it is about -0.3% of the ionization potential of the gold atom. For heavy elements it cancels about one percent of the kinetic relativistic effects, included in the Dirac eq uation. In this sense the earlier work during over two decades was at least 99% correc t. This collaboration with St. Petersburg State University continues.

Fig. 1. The structure of the species [ HC(AuPH₃)_4] ⁺ with a huge proton binding energy of about 1200 kJ/mol (Pyykkö, P. and Tamm, T.)(9).

Fig. 2. What does beryllium actually do in basic solutions? One stru cture found for beryllium in basic solutions is [ Be₄(OH)_10] ^2-. (Schmidbaur, H. Schmidt, M., Schier, A., Riede, J., Tamm, T. < /B>and Pyykkö, P.)(11).