Waclaw Kolodziejski

Solid-state NMR study of ordered mesoporous aluminosilicate MCM-41 synthesized on a liquid-crystal template

A novel mesoporous aluminosilicate MCM-41, synthesized in a liquid-crystal system, was characterized by magic angle spinning NMR. Conventional Bloch decay and cross-polarization spectra were compared. The 27Al spectra showed that the calcined material was highly siliceous, while 29Si NMR proved that it was rich in single and geminal silanol groups. Two kinds of the silanol groups were detected: exchanging and non-exchanging protons with water on the timescale of the 1H experiment. The 13C spectra of the uncalcined material were consistent with the concept of the micellar arrangement of the cetyltrimethylammonium template inside MCM-41.

Infrared spectroscopy, thermoprogrammed desorption, and nuclear magnetic resonance study of the acidity, structure, and stability of zeolite MCM-22

Abstract Zeolite MCM-22 has been studied by infrared (i.r.) spectroscopy, thermoprogrammed desorption (t.p.d.) of NH 3 , and 27 Al n.m.r. with magic angle spinning ( MAS ). It has been found that zeolites MCM-22 and ZSM-5 both have framework i.r. bands at about 1,245 and 550 cm −1 , and zeolites MCM-22 and Y both have two pore opening i.r. bands at about 380 and 317 cm −1 . In MCM-22 there are two kinds of bridged hydroxyls (3,620 and 3,575 cm −1 ) and two kinds of internal silanols (3,500 and 3,700 cm −1 ). The latter two i.r. frequencies are similar to those in zeolites ZSM-5 and Y, respectively. 27 Al n.m.r. reveals two kinds of framework tetrahedral Al. The spectroscopic similarities and the dual appearance of the relevant i.r. bands/n.m.r. peaks seem to indicate that MCM-22 probably has two distinct pore systems containing 10- and 12-member rings, which is in accordance with our recently published results of catalytic tests. Quantitative results on Bronsted and Lewis acidity are reported from the i.r. study of pyridine adsorption and from t.p.d. of NH 3 . The Bronsted sites are strongly acidic and accessible for pyridine. MCM-22 is very sensitive to the calcination conditions, being more dealuminated on heating in air than in a vacuum or N 2 . The dealumination occurs even during grinding in a mortar with a concomitant decrease in the acidity of the final sample.

Solid-State NMR Studies of Bone

Solid-state NMR studies on bone, bone mineral standards and collagen are reviewed. NMR spectroscopy was mostly applied to the bone mineral and confirmed that the structure resembles that of calcium carbonatoapatite of type B. Apatite in bone was found to be deficient in structural hydroxyl groups. Concentration and distribution of hydrogenphosphate and carbonate ions, and of water in apatite crystals (interior vs surface and crystal defects vs structural positions) were closely investigated. The NMR characterization of the organic matrix still remains a challenge for future research.

Kinetics of 1H 31P NMR cross-polarization in bone apatite and its mineral standards

Kinetics of NMR cross‐polarization (CP) from protons to phosphorus‐31 nuclei was studied in the following samples: mineral of whole human bone, apatite prepared from bone, natural brushite, synthetic hydroxyapatite (hydrated and calcined), and synthetic carbonatoapatite of type B with 9 wt% of CO32−. In order to avoid an effect of magic angle spinning on CP and relaxation, the experiments were carried out on static samples. Parameters of the CP kinetics were discussed for trabecular and cortical bone tissue from adult subjects in comparison to the synthetic mineral standards. It was found that carbonatoapatite shows similar CP behavior to the bone mineral. Both materials undergo two‐component CP kinetics. The fast‐relaxing classical component is from the surface of apatite crystals and the slow‐relaxing nonclassical component comes from the crystal interior. The components have been unambiguously assigned using inverse CP from phosphorus‐31 to protons. The study provides information on a structured water layer, which covers crystal surface of carbonato‐ and bone apatite. The layer encompasses ca 40% of apatite phosphorus and its thickness is more than ca 2 nm. Copyright

Synthesis and Structural Analysis of Polyester Prodrugs of Norfloxacin

Two-, three- and four-arm, star-shaped poly(ε-caprolactone) and poly(D,L‑lactide) homopolymers, and copolymers of ε-caprolactone with D,L-lactide were synthesized via ring-opening polymerization of cyclic esters in the presence of glycerol, penthaerythritol and poly(ethylene glycol) as initiators and stannous octoate as a catalyst. Thus obtained oligomers were successfully used in the synthesis of novel macromolecular prodrugs of norfloxacin. The structures of the polymers and prodrugs were elucidated by means of MALDI-TOF MS, NMR and IR studies.

Polymerization of Cyclic Esters Initiated by Carnitine and Tin (II) Octoate

Low-molecular weight poly(ε-caprolactone), polylactides and copolymers of ε−caprolactone and lactides were obtained by the polymerization of cyclic esters in the presence of a carnitine/SnOct2 system. Their structures were proven by means of MALDI−TOF, IR and NMR studies. Effects of temperature, reaction time and carnitine dosage on the polymerization process were examined.

NOTE: Polymerization of Cyclic Esters Using Aminoacid Initiators

The low-molecular weight poly(ϵ -caprolactone) and polylactide were obtained by the polymerization of cyclic esters in the presence of amino acid initiators. The polymer structures were elucidated by means of MALDI TOF, NMR and IR studies. Effects of temperature, reaction time and initiator dosage on the polymerization process were examined.

Concentration of hydroxyl groups in dental apatites: a solid-state 1H MAS NMR study using inverse 31P → 1H cross-polarization

The concentration of structural hydroxyl groups in the apatite mineral of enamel, dentin and cementum of healthy human teeth was estimated by reference to stoichiometric hydroxyapatite to be 73 +/- 3, 18 +/- 2 and 18 +/- 1%, respectively.

Comparative Proton Nuclear Magnetic Resonance Studies of Amantadine Complexes Formed in Aqueous Solutions with Three Major Cyclodextrins

Host-guest complexes of alpha-, beta-, and gamma-cyclodextrins (α-CD, β-CD, and γ-CD, respectively) with amantadine (1-aminoadamantane, AMA; an antiviral agent) were characterized in aqueous solutions using proton nuclear magnetic resonance (NMR) spectroscopy. Host-guest molecular interactions were manifested by changes in the chemical shifts of AMA protons. NMR Jobs plots showed that the stoichiometry of all the studied complexes was 1:1. Two-dimensional T-ROESY experiments demonstrated that the complexes were formed by different degrees of incorporation of the adamantyl group of AMA into the CD cavity. The mode of AMA binding was proposed. The AMA molecule came into the α-CD cavity (the smallest size) or β-CD cavity (the intermediate size) through its wide entrance to become shallowly or deeply accommodated, respectively. In the complex of AMA with γ-CD (the largest cavity size), the adamantyl group was also quite deeply inserted into the CD cavity, but it arrived there through the narrow cavity entrance. It was found that the adamantyl group of AMA was best accommodated by the β-CD cavity. The binding constants Kaa of the studied complexes (in M(-1) ), determined from DOSY NMR, were fairly high; their values in an ascending order were: α-CD (183) < γ-CD (306) ≪ β-CD (5150).

31P solid-state NMR study of spin diffusion in the molecular sieve VPI-5 using variable-speed MAS

Abstract Hydrated aluminophosphate molecular sieve VPI-5 has been studied by 31 P solid-state NMR with variable-speed magic-angle spinning. Cross-polarization and two-dimensional spin-diffusion spectra were used to assign NMR signals to particular phosphorus sites in the structure in the P6 3 space group. The aim was to assess the value of the technique for the study of phosphate molecular sieves.