Main research interest is focused at present on the theoretical (computational) studies of ligands (organic compounds) and their interactions with metal ions in water with a main focus on:
a) Fundamental physical properties controlling the strength of complexes formed. Our main focus is on (i) intramolecular (bonding) interactions and this includes the H-clashes in metal complexes, (ii) intramolecular strain, (iii) atomic energies, (iv) bond order by use of the delocalization index, etc.
b) Theoretical interpretation of experimental trends in formation constants.
c) Theoretical prediction of protonation constants.
d) Theoretical prediction of formation constants.
e) Theoretical prediction of protonation sequence; linear polyamines and bisphosphonates are being investigated at present.
Computational techniques used at present are: Gaussian 09, ADF, QTAIM of Bader (AIMAll software), charge and energy decomposition technique ETS-NOCV.
We are also involved in the experimental investigations and this involves the determination of protonation constants, formation constants, growing crystals of protonated ligands and complexes of interest, Raman and IR spectroscopies. Among compounds of special interest are bisphosphonates used commercially in the treatment of bone cancer, such as HEDP, risedronic acid and the most potent one, zoledronic acid.
1. C.E. Skopec, I. Cukrowski and H.M. Marques, “Using Artificial Neural Networks to Develop Molecular Mechanics Parameters for the modelling of metalloporphyrins. IV. Five- and six-coordinate metalloporphyrins of Mn, Co, Ni and Cu, J. Mol. Struct. 783, 1-3 (2006) pp. 21-33.
2. C.M.M. Machado, I. Cukrowski and H.M.V.M. Soares, “Interpretation of non-Nernstian slopes in graphic analysis of data collected in pH-range close to deprotonation of a ligand. Part I. A glass electrode potentiometric and polarographic study of Cd–(TAPSO)x–(OH)y and Zn–(TAPSO)x–(OH)y systems”, Talanta 68 (2006) 819-830.
3. C.M.M. Machado, I. Cukrowski and H.M.V.M. Soares, “Complex formation in the region of metal hydrolysis and M(OH)2 precipitation. A glass electrode potentiometric and polarographic study of Cd-(AMPSO)x-(OH)y and Zn-(AMPSO)x-(OH)y systems”, Electroanalysis, 18 (2006) No. 7, 719-729.
4. J. Robinson, I. Cukrowski and H.M. Helder, “Modelling the interaction of several bisphosphonates with hydroxylapatite using the generalised AMBER Force Field”, J. Mol. Struct., 825 (2006) 134-142.
5. I. Cukrowski, P. Magampa , and T. S. Mkwizu, ‘Voltammetry as Virtual Potentiometric Sensor in Modelling of a Metal/Ligand System and Refinement of Stability Constants. Part 5. Complexation Studies of Hydrolysis-Prone Lead(II) with Glycine and Sarcosine by Sampled-Direct-Current Polarography Involving Virtual Potential', Helv. Chim. Acta, 89 (2006) 2934-2952.
6. I Cukrowski, HM. Marques, T Mkwizu, PP. Magampa, and C Serge, “Influence of electronic and steric effects on stability constants and electrochemical reversibility of divalent ion complexes with glycine and sarcosine. A glass electrode potentiometric, sampled direct current polarographic, virtual potentiometric, and molecular modelling study”, Anal. Chim. Acta 590 (2007) 203-216.
7. I. Cukrowski, L. Popoviæ, W. Barnard, S. Paul, P.H. van Rooyen, D.C. Liles, “Modelling and spectroscopic studies of bisphosphonate-bone interactions. The Raman, NMR and crystallographic investigation of Ca-HEDP complexes”. Bone, 41 (2007) 668-678.
8. A.S. de Sousa, M.A. Fernandes, W. Nxumalo, J.L. Balderson, T.Jeftiè, I. Cukrowski and H.M. Marques, “Sc(III) porphyrins. The molecular structure of two Sc(III) porphyrins and a re-evaluation of the parameters for the molecular mechanics modelling of Sc(III) porphyrins”, J. Mol. Struct. 872 (2008) 47-55.
9. P.R. Varadwaj, I. Cukrowski and H.M. Marques, “DFT-UX3LYP Studies on the Coordination Chemistry of Ni2+. Part 1: Six Coordinate [Ni(NH3)n(H2O)6-n]2+ Complexes”, J. Phys. Chem. A, 112 (2008) 10657-10666.
10. J.M. Wagener, M.K. Dithebe, D. Mogano, I. Cukrowski and J.R. Zeevaart, “Modelling of the Blood Plasma Species of Biguanide Derivatives Exhibiting Potential as Diagnostic Radiopharmaceuticals”, S. Afr. J. Chem., 61 (2008) 82–92.
11. P.R. Varadwaj, I. Cukrowski, and H.M. Marques, “Low-Spin Complexes of Ni2+ with Six NH3 and H2O Ligands: a DFT-RX3LYP study”, J. Mol Struct. (THEOCHEM) 902 (2009) 21–32.
12. C. Billing and I. Cukrowski, “Glass Electrode Calibration for Use in the Voltammetric Determination of Stability Constants under Extreme Acidic Conditions”, SA J Chem., 62 (2009) 168-178.
13. W. Barnard, S.O. Paul, P.H. van Rooyen and I. Cukrowski, “The analysis of pH dependent protonated conformers of 1-hydroxyethylidene-1,1-diphosphonic acid by means of FT-Raman Spectroscopy, multivariate curve resolution and DFT modelling”, J. Raman Spectroscopy, 40 (12) (2009) 1935-1941.
14. K. Govender and I. Cukrowski, “Density functional theory in prediction of four stepwise protonation constants for nitrilotripropanoic acid (NTPA)”, J. Phys. Chem. A, 113 (2009) 3639–3647.
15. P.R. Varadwaj, I. Cukrowski, and H.M. Marques, “DFT RX3LYP and RPBEPBE studies on the structural, electronic, and vibrational properties of some amino-alcohol ligands”, J. Mol Struct. (THEOCHEM), 915 (2009) 20-32.
16. T.S. Mkwizu, M.K. Mathe, and I. Cukrowski, “Automated electrodeposition of bimetallic noble-metal nanoclusters via redox-replacement reactions for electrocatalysis”, ECS Trans., 19 (24) (2009) 97-113.
17. J.R Zeevaart, J.M. Wagener, M. Neves, M.C. Costa, C. Rodrigues, M. Dithebe, E. Kilian, and I. Cukrowski, “99mTc-labelled biguanide derivatives: chemical speciation modelling thereof and evaluation in vervets”, J Radioanal. Nucl. Chem. 283 (2010) 123-131.
18. T.S. Mkwizu, M.K. Mathe, and I. Cukrowski, “Electrodeposition of multilayered bimetallic nanoclusters of ruthenium and platinum via surface–limited redox–replacement reactions for electrocatalytic applications”, Langmuir 26 (2010) 570-580.
19. K. Govender and I. Cukrowski, “Density Functional Theory and Isodesmic Reaction Based Prediction of Four Stepwise Protonation Constants, as log KH(n), for Nitrilotriacetic Acid. The Importance of a Kind and Protonated Form of a Reference Molecule Used”, J. Phys. Chem. A, 114 (2010) 1869-1878.
20. I. Cukrowski and K. K. Govender, “A Density Functional Theory- and Atoms in Molecules-based Study of NiNTA and NiNTPA Complexes toward Physical Properties Controlling their Stability. A New Method of Computing a Formation Constant”, Inorg. Chem. 49 (2010) 6931-6941.
21. I. Cukrowski and C.F. Matta, “Hydrogen-Hydrogen Bonding: A Stabilizing Interaction in Strained Chelating Rings of Metal Complexes in Aqueous Phase”, Chem. Phys. Lett. 499 (2010) 66–69.
22. M.K. Nieuwoudt, J.D. Comins and I. Cukrowski, “The growth of the passive film on iron in 0.05 M NaOH studied in situ by Raman micro-spectroscopy and electrochemical polarisation. Part I: Near Resonance Enhancement of the Raman spectra of iron oxide and oxyhydroxide compounds”, J Raman Spectroscopy, (2010), DOI:10.1002/jrs.2837.
23. M.K. Nieuwoudt, J.D. Comins and I. Cukrowski, “The growth of the passive film on iron in 0.05 M NaOH studied in situ by Raman micro-spectroscopy and electrochemical polarisation. Part II: In situ Raman Spectra of the passive film surface during growth by electrochemical polarization”, J Raman Spectroscopy, (2010), DOI:10.1002/jrs.2842.
24. I. Cukrowski and C.F. Matta, “Protonation sequence of linear aliphatic polyamines from intramolecular atomic energies and charges”, Comp. Theoret. Chem., 966 (2011) 213–219.
25. P.R. Varadwaj, I. Cukrowski, C.B. Perry and H.M. Marques, “A Density Functional Theory and Quantum Theory of Atoms in Molecules Analysis of the stability of Ni(II) complexes of some amino Aalcohol ligands”, J. Phys. Chem. A 115 (2011) 6629–6640.
26. I. Cukrowski, K.K. Govender, M.P. Mitoraj and M. Srebro, “QTAIM and ETS-NOCV analyses of intramolecular CH•••HC interactions in metal complexes”, J. Phys. Chem. A, (2011), DOI: 10.1021/jp203797y.