Janusz Serwatowski

Bio: Janusz Serwatowski is an academic researcher from Warsaw University of Technology. The author has contributed to research in topics: Hydrogen bond & Crystal structure. The author has an hindex of 20, co-authored 104 publications receiving 1144 citations. Previous affiliations of Janusz Serwatowski include University of Warsaw.

Regiospecific metalation of oligobromobenzenes.

Abstract: The metalation of selected oligobromobenzenes with lithium diisopropylamide (LDA) was investigated. 1,3-Dibromo-substituted benzenes were metalated without special precautions since the resultant 2,6-dibromophenyllithium intermediates are relatively stable under reaction conditions: corresponding benzaldehydes were obtained in good or moderate yields after subsequent quench with N,N-dimethylformamide (DMF). Aryllithium compounds derived from 1,4- and 1,2-dibromobenzene are much less stable, but they could be trapped by the in situ use of chlorotrimethylsilane. The one-pot metalation/disilylation of 1,4-dibromo- and 1,2-dibromobenzene afforded 1,4-dibromo-2,5-bis(trimethylsilyl)benzene and 2,3-dibromo-1,4-bis(trimethylsilyl)benzene, respectively.

Structural and Energetic Landscape of Fluorinated 1,4-Phenylenediboronic Acids

Abstract: The results of X-ray crystallographic and computational studies of a series of fluorinated 1,4-phenylenediboronic acids (i.e., fluoro-1,4-phenylenediboronic acid, 2,6-difluoro-1,4-phenylenediboronic acid, 2,3-difluoro-1,4-phenylenediboronic acid, 2,5-difluoro-1,4-phenylenediboronic acid, and tetrafluoro-1,4-phenylenediboronic acid) are reported. The effect of fluorine substitution on crystal organization in the presence of strong and directional hydrogen bonds was studied. Comparison with the two previously reported forms of the unsubstituted 1,4-phenylenediboronic acid revealed a strong relation between a supramolecular network and the number of water molecules present in the crystal lattice. As indicated by the theoretical calculations performed in the CRYSTAL and PIXEL programs, the structures with greater amount of water are better stabilized (from about −170 kJ·mol–1 for anhydrous forms to about −420 kJ·mol–1 for tetrahydrate). The energy of hydrogen bonded dimers vary from −40 kJ·mol–1 to −50 kJ·mol...

A tautomeric equilibrium between functionalized 2-formylphenylboronic acids and corresponding 1,3-dihydro-1,3-dihydroxybenzo[c][2,1]oxaboroles

Abstract: Functionalized 2-formylphenylboronic acids undergo an unprecedented tautomeric rearrangement in solution to form corresponding 1,3-dihydro-1,3-dihydroxybenzo[c][2,1]oxaboroles. X-Ray analyses of selected examples revealed diverse solid-state molecular structures from a planar open form with a hydrogen-bonded carbonyl group (X = 3-F) through a twisted conformer showing a weak carbonyl–boron interaction (X = 3,5-Br2) to a cyclic oxaborole derivative (X = 3-Br). Variable-temperature 1H NMR spectroscopy was used to determine equilibrium constants as well as enthalpies and entropies of tautomerization in a mixed solvent [D6]acetone–D2O (95 : 5). A computational approach to the process by DFT (B3LYP) and MP2 methods has also been performed.

Highly Fluorescent Red-Light Emitting Bis(boranils) Based on Naphthalene Backbone

Abstract: Ten bis(boranils) differently substituted at the boron atom and iminophenyl groups were synthesized from 1,5-dihydroxynaphthalene-2,6-dicarboxaldehyde using a simple one-pot protocol. Their photophysical properties can be easily tuned in a wide range by the variation of substituents. Their absorption and emission spectral bands are significantly red-shifted (λmax = 495–590 nm, λem = 533–683 nm) when compared with simple boranils, whereas fluorescence quantum yields are strongly improved to reach 83%. The attachment of pendant NO2 and NEt2 groups at the opposite positions of the π-conjugated bis(boranil) scaffold resulted in the formation of an unprecedented system featuring push–pull architecture.

Bromine as the ortho-directing group in the aromatic metalation/silylation of substituted bromobenzenes.

Abstract: The one-pot metalation/disilylation of selected bromobenzenes bearing electron-withdrawing substituents p-, m-, o-XC6H4Br (X = F, Cl, I, CN, CF3) using 2 equiv of lithium diisopropylamide (LDA) and 2 equiv of chlorotrimethylsilane (TMSCl) was investigated. The best results of disilylation were obtained for para-substituted bromobenzenes, but the regioselectivity of the reaction is strongly influenced by the ortho-directing power of the substituent. On the contrary, the disilylation of meta-substituted bromobenzenes was not efficient or even failed in some cases and hence monosilylated derivatives were isolated as major or sole products. Diverse reactivity was observed for ortho-substituted bromobenzenes, e.g., 2-bromobenzonitrile and 2-bromochlorobenzene, were converted into corresponding disilylated derivatives in a high and moderate yield, respectively, whereas 1-bromo-2-(trifluoromethyl)benzene underwent only monosilylation.

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Luminescent materials: locking π-conjugated and heterocyclic ligands with boron(III).

Abstract: Multidisciplinary research on novel organic luminescent dyes is propelled by potential applications in plastic electronics and biomedical sciences. The construction of sophisticated fluorescent dyes around a tetrahedral boron(III) center is a particular approach that has fueled the creativity of chemists. Success in this enterprise has been readily achieved with simple synthetic protocols, the products of which display unusual spectroscopic behavior. This account is a critical review of recent advances in the field of boron(III) complexes (excluding BODIPYs and acetylacetonate boron complexes) involving species displaying similar coordination features, and we outline their potential development in several disciplines.

PASCal: a principal axis strain calculator for thermal expansion and compressibility determination

Abstract: This article describes a web-based tool (PASCal; principal axis strain calculator; http://pascal.chem.ox.ac.uk) designed to simplify the determination of principal coefficients of thermal expansion and compressibilities from variable-temperature and variable-pressure lattice parameter data. In a series of three case studies, PASCal is used to reanalyse previously published lattice parameter data and show that additional scientific insight is obtainable in each case. First, the two-dimensional metal–organic framework [Cu2(OH)(C8H3O7S)(H2O)]·2H2O is found to exhibit the strongest area negative thermal expansion (NTE) effect yet observed; second, the widely used explosive HMX exhibits much stronger mechanical anisotropy than had previously been anticipated, including uniaxial NTE driven by thermal changes in molecular conformation; and third, the high-pressure form of the mineral malayaite is shown to exhibit a strong negative linear compressibility effect that arises from correlated tilting of SnO6 and SiO4 coordination polyhedra.