Application of antiscalants is a worldwide practice for industrial scale formation mitigation. The range of reagents is constantly expanding, and new scale inhibitors are permanently elaborated, including biodegradable ones. An antiscalant-driven scale inhibition theory has formed in the mid-twentieth century, and is up to date with some minor refinements. However, in recent years, the classical views have been increasingly criticized on the grounds of such modern methods as dynamic light scattering, particle counter technique and fluorescent visualization of antiscalant location in industrial and model system's deposits. These methods provide a better understanding of scale inhibition mechanisms. In a present review the major mechanisms of scale inhibition are critically examined, and a hypothesis on the dominating role of solid impurities interaction with antiscalant is formulated. According to this hypothesis, the scale crystals nucleation in the bulk aqueous medium is a heterogeneous process, catalyzed by foreign solid nano/microdust particles, serving as crystallization templates (seeds). Thus, an antiscalant competes for these templates with the scale forming ions, blocks the background seeds, and reduces therefore the number of potential crystallization centers. In this way, the scale inhibitor slows down the scale formation due to the foreign seeds isolation, but not via direct interaction with the nuclei of a sparingly soluble salt.

The cation-induced dimerization of tetra-(15-crown-5)-substituted Al(III) phthalocyaninate with Na + , K + and Rb + salts in solution has been studied by 1 H NMR. It has been demonstrated that two types of supramolecular dimers coexist in solutions, which is consistent with the existence of both the monomeric and oxygen-bridged dimeric forms of the initial Al(III) complex. With the use of mass spectrometry (MALDI-TOF and HR-ESI), it has been shown that Al(III) monophthalocyaninate [(OH)AlR 4 Pc] forms supramolecular dimers {[M 4 (XAlR 4 Pc) 2 ] 4+ (X − ) 4 }, whereas Al(III) μ-oxodiphthalocyaninate [(AlR 4 Pc) 2 (μ-O)] forms oxygen-bridged supramolecular dimers {[M 4 (XAlR 4 Pc) 2 (μ-O)] 2+ (X − ) 2 }.

The dynamic light scattering (DLS) special technique is used to study the bulk supersaturated gypsum aqueous solutions during the induction period in 0.2 mol.dm(-3) NaCl at pH 9 and 25 degrees C. It is based on the standard SiO2 nanoparticles (Ludox TM40) injection into the supersaturated gypsum solution. These nanoparticles act as an internal indifferent light scattering intensity reference and provide a semiquantitative measurement of a relative gypsum particles content in a blank solution and in the system treated with amino-tris(methylenephosphonic acid), ATMP. It is found that ATMP sufficiently reduces the number of gypsum nuclei, spontaneously formed in the supersaturated solutions. In a parallel way the chemical forms of antiscalant in the experimental systems have been modeled. A tentative nonconventional mechanism of scale inhibition is proposed. It assumes that the active crystal formation centers already exist in any analytical grade aqueous solution in the form of solid nanoimpurities with a size ranging from one to several hundred nm. The ATMP antiscalant competes with Ca2+ and SO42-. for these centers and blocks them. Therefore the number of gypsum growth centers diminishes significantly. Thus the concentration of corresponding CaSO4.2H(2)O particles gets reduced at least 10-fold. The collision rate of such particles decreases 100-fold. This explains both induction time prolongation by ATMP and sub-stoichiometry of its efficacy.

A comparative ability of industrial samples of four phosphorus-free polymers (polyaspartate [PASP]; polyepoxysuccinate [PESA]; polyacrylic acid sodium salt [PAAS]; and copolymer of maleic and acrylic acid [MA-AA]) and of two phosphonates (aminotris(methylenephosphonic acid), ATMP; 1-hydroxyethane-1,1-bis(phosphonic acid), HEDP) to inhibit calcium carbonate precipitation is tested following the National Association of Corrosion Engineers (NACE) Standard TM0374-2007 for the dosages ranging from 1 to 25 mg u dm-3. In a parallel way, an aqueous phase is studied by dynamic light scattering (DLS), while the solid calcium carbonate is characterized by scanning electron microscopy and powder X-ray diffraction (XRD). The following ranking ATMP > HEDP > PESA (400-1,500 Da) similar to PASP (1,000-5,000 Da) > PAAS (3,000-5,000 Da) similar to MA-AA is found. DLS exhibits the formation of CaCO3 particles with a particle size around 300-400 nm in the blank solution as well as in presence of all antiscalants immediately after a supersaturated solution preparation with negative zeta-potential around -5 mV for all reagents. Only for MA-AA the bigger aggregates are formed. XRD analysis revealed calcite formation at low dosages of all antiscalants, although the crystal shapes are distorted. At a higher concentration of some antiscalants, aragonite (PAAS, ATMP) and vaterite (PASP) are found to be the dominating crystal modifications. The differences between the blank experiments and scaling in the presence of inhibitor are attributed neither to CaCO3 particle size nor to electrostatic charge, but to the number of particles formed. In presence of an antiscalant, the number of solid phase particles is sufficiently less, than in a blank solution. Thus, both the polymers and phosphonates prevent mostly the formation of initial crystallization centers under NACE protocol conditions.

A relative ability of industrial samples of four phosphorus-free polymers (polyaspartate (PASP); polyepoxysuccinate (PESA); polyacrylic acid sodium salt (PAAS); copolymer of maleic and acrylic acid (MA-AA)) and of three phosphonates (aminotris(methylenephosphonic acid), ATMP; 1-hydroxyethane-1,1-bis(phosphonic acid), HEDP; phosphonobutane-1,2,4-tricarboxylic acid, PBTC) to inhibit calcium sulfate precipitation is studied following the NACE Standard along with dynamic light scattering (DLS), scanning electron microscopy (SEM), and X-ray diffraction (XRD) technique. For the 0.5 mg·dm−3 dosage, the following efficiency ranking was found: MA-AA~ATMP>PESA (400–1500 Da)>PASP (1000–5000 Da) ≫ PAAS (3000–5000 Da)~PBTC~HEDP. The isolated crystals are identified as gypsum. SEM images for PESA, PASP, PAAS, and HEDP and for a blank sample indicated the needle-like crystal morphology. Surprisingly, the least effective reagent PBTC revealed quite a different behavior, changing the morphology of gypsum crystals to an irregular shape. The DLS experiments exhibited a formation of 300 to 700 nm diameter particles with negative ζ-potential around −2 mV for all reagents. Although such ζ-potential values are not capable of providing colloidal stability, all three phosphonates demonstrate significant gypsum particles stabilization relative to a blank experiment.

Scale formation is a challenge worldwide. Recently, scale inhibitors represent the best solution of this problem. The polyaminocarboxylic acids have been the first to be successfully applied in the field, although their efficacy was rather low. The next generation was developed on the grounds of polyphosphonic acids. The main disadvantage of these is associated with low biodegradation level. Polyacrylate-based phosphorous free inhibitors proposed as an alternative to phosphonates all also had low biodegradability. Thus, the main trend of recent R&D is the development of a new generation: environmentally friendly biodegradable scale inhibitors. The recent state of the word and domestic scale inhibitors markets is considered, the main industrial inhibitors manufacturers and marketed substances, as well as the general trends of R&D in the field, are characterized. It is demonstrated that most research is focused on biodegradable polymers and on phosponates with low phosphorus content, as well as on implementation of biodegradable fragments into polyacrylate matrixes for biodegradability enhancement. The problem of research results comparability is indicated along with domestic-made inhibitors quality and the gaps in scale inhibition mechanism. The actuality of fluorescent indicator fragment implementation into the scale inhibitor molecule for the better reagent monitoring in a cooling water system is specially emphasized.

The formation of μ-oxo and μ-fluoro dimers based on aluminum tetra-15-crown-5-phthalocyanine Al[(15C5) 4 PcX], X = OH, OCH 3 ( I ) was studied by UV-Vis and 1 H NMR spectroscopy. It is established that the formation of μ-oxo dimer (μ-O)[(15C5) 4 PcAl] 2 in chloroform solution occurs upon titration of I with methanol, ethanol, and dimethylsulfoxide, as well as at the Al 2 O 3 -eluent interphase, upon an increase of the methanol concentration in chloroform and upon storage of I in the solid state. It is shown for the first time that the interaction of [(15C5) 4 PcAl(OH)] with tetrabutylammonium fluoride in chloroform results in the formation of stable μ-fluoro dimer of (μ-F)[(15C5) 4 PcAl] 2 + , structure of which identified based on UV-Vis, 1 H NMR, and MALDI-TOF mass spectral data. Conditions for preparation of complex [(15C5) 4 PcAlF 2 ] − in solutions are found, and the possibility of sequential transformations in the series of complexes [(15C5) 4 PcAl](OH) → [(15C5) 4 PcAlF 2 ] − → (μ-F)[(15C5) 4 Pcal] 2 + is shown.

Методом электронной спектроскопии поглощения и 1H ЯМР-спектроскопии изучены процессы формирования -оксо и -фторо-димеров на основе тетра-15-краун-5-фталоцианина алюминия Al[(15C5)4PcX], X = OH, OCH3 (I). Установлено, что образование -оксо-димера в растворе хлороформа происходит при титровании I метанолом, этанолом, диметилсуфоксидом, а также при хроматографической очистке на Al2O3 с увеличением полярности элюента и при хранении I в твердом виде. Впервые показано, что взаимодействие [(15C5)4PcAl(OH)] с фторидом тетрабутиламмония в хлороформе приводит к образованию устойчивого -фторо-димера состава идентифицированного по данным ЭСП, 1H ЯМР и MALDI-TOF масс-спектрометрии. Найдены условия получения комплекса состава [(15C5)4PcAlF2]- в растворах, а также показана возможность последовательных превращений в ряду комплексов состава [(15C5)4PcAl](OH) [(15C5)4PcAlF2]- .

The cation-induced aggregation of sandwich crown-substituted complexes [Ln(R4Pc)2] (Ln = Lu (I) and Yb (II), R4Pc2− is the 4,5,4′,5′,4″,5″,4‴,5‴-tetrakis(1,4,7,10,13-pentaoxatridecamethylene)phthalocyaninate ion) and Ln2(R4Pc)3(Ln = Lu (III) and Yb (IV) in a CDCl3-DMSO-d 6 solution has been studied by 1H NMR. The data obtained are consistent with the conclusions concerning the composition of supramolecular aggregates drawn from spectrophotometric titration data. The molecules of double-decker complexes I and II form supramolecular oligomers, whereas triple-decker complexes III and IV form supramolecular dimers, which is presumably due to the stronger distortion of the planes of the outer decks of the triple-decker complexes as compared to their double-decker analogues.

The scandium(III) complexes with tetra(15-crown-5)phthalocyanine [Sc(R 4 Pc) 2 ] ·0 ( I ) and Sc(R 4 Pc) · OAc ( II ) have been synthesized by condensation of Sc 3+ with phthalocyanine H 2 R 4 Pc (4,5,4′,5′,4″,5″,4‴,5‴-tetrakis(1,4,7,10,13-pentaoxatridecamethylene)phthalocyanine). Compounds I and II have been characterized by spectral methods: electronic absorption spectroscopy, MALDI-TOF MS, IR spectroscopy, and 1 H NMR. The redox properties of I and the photoluminescent properties of II have been studied.

Синтезированы комплексы Sc(III) с тетра(15-краун-5)фталоцианином составов [Sc(R4Pc)2].0 (I) и Sc(R4Pc) · OAc (II) методом конденсации Sc3+ c фталоцианином, H2R4Pc (4, 5, 4, 5, 4, 5,4, 5 -тетракис(1, 4, 7, 10, 13 – пентаоксатридекаметилен)фталоцианин). Соединения I и II охарактеризованы спектральными методами: ЭСП, MALDI-TOF-MS, ИК, ЯМР1H. Изучены окислительно-восстановительные свойства [Sc(R4Pc)2].0, а также фотолюминесцентные свойства Sc(R4Pc) · OAc.

The products of 4′,5′-dibromobenzo-15-crown-5 ( I ) cyanation by the Rosenmund-Braun reaction are studied by the 1 H NMR and IR spectroscopy methods. X-ray diffraction analysis of two isolated products, i.e., di(4′,5′-dicyanobenzo-15-crown-5) 1.6 hydrate {(CN) 2 B15C5} 2 · 1.6H 2 O ( IIa ) and 4′,5′-dicyanobenzo-15-crown-5,4′-cyano-5′-cyano(bromo)benzo-15-crown-5 dihydrate (CN) 3.85 Br 0.15 (B15C5) 2 · 2H 2 O ( III ) is performed. Crystals IIa are monoclinic, a = 15.882(2) Å, b = 11.412(2) Å, c = 18.484(3) Å, β = 100.717(3)°, V = 3291.7(9) Å 3 , Z = 4, space group P 2 1 / c, R = 0.0746 for 4775 reflections with I > 2σ( I ). Crystals III are monoclinic, a = 15.956(3) Å, b = 11.425(2) Å, c = 18.865(4) Å, β = 99.32(3)°, V = 3394(1) Å 3 , Z = 4, space group P 2 1 / c, R = 0.0692 for 2070 reflections with I > 2σ( I ). Compounds IIa and III have similar structures with two crystallographically independent molecules in each ( A and B in IIa ; C and D in III ). Four of the five O atoms of a macrocycle in molecules A and C form hydrogen bonds with the water molecules. The latter molecules lie above and below the cycle plane at a distance of ∼2 Å from this plane. The A and C molecules have identical conformations ( TTG TTG TTG TTG TTC ) that differ from those of molecules B ( TTG TGG STT SSG TTC ) and D ( TTC TSG STT SSG TTC ).

Tris[tetra(15-crown-5)phthalocyaninato]dilutetium(III) ( R 4 Pc )3 Lu 2, whose structure had been confirmed earlier by X-ray analysis, was further examined by physicochemical studies. The redox properties of this complex were investigated by cyclic voltammetry. The spectroelectrochemical study of this compound has been performed for the first time. Based on the results obtained and analysis of literature data, an electrochemical criterion related to double- and triple-decker structure of lanthanide phthalocyanines has been proposed. IR and 1 H NMR data are also reported.

The cation-induced supramolecular organization of sandwich crown-substituted rare-earth phthalocyaninates in organic solvents in the presence of alkali-metal thiocyanates has been studied by spectrophotometry. KSCN reacts with a triple-decker lutetium complex in CHCl3 to form the cofacial dimers 2Lu(2)(R4Pc)(3).4KSCN (R4Pc2- = 4,5,4',5',4", 5",4"', 5"'-tetrakis(1,4,7,10,13-pentaoxatridecamethylene)phthalocyaninate ion). The nitrogenous base 1,8-diazabicyclo[5.4.0]undec-7-ene can reduce monoradical rare-earth phthalocyaninate (Y3+ Gd3+, Yb3+, Lu3+). The interaction of alkali-metal (K+, Rb+, Cs+) thiocyanates with one-electron-reduced diphthalocyaninates forms contributes to their organization in polymeric cofacial aggregates with the composition { [Ln(R4Pc)(2)(-) . M+] . 3MSCN}(N).

The reaction of tetra(15-crown-5)-substituted phthalocyaninate of lutetium acetate (I) with sodium and potassium acetates in a CHCl3-DMSO solvent mixture was studied by spectrophotometry and H-1 NMR spectroscopy. The crown-ether moiety of I was found to chelate K+ and Na+ ions. The reaction of I with K+ results in the formation of coaxial dimers of the "host-guest" type, whereas the reaction with Na+ yields no dimers of this type.

A double-decker complex of yttrium(III) with tetra-15-crown-5-phthalocyanine has been synthesised and characterised by spectroscopic methods.

An original method based on metal-free ligand and lanthanide acetate direct interaction in the presence of a strong organic base (DBU) is used to prepare sandwich-type gadolinium and ytterbium crown-ether substituted phthalocyanines bis[4,5,4′,5′,4″,5″,4‴,5‴-tetrakis(1,4,7,10,13-pentaoxatridecamethylene)phthalocyaninato]gadolinium (ytterbium) and tris[4,5,4′,5′,4″,5″,4‴-,5‴-tetrakis(1,4,7,10,13-pentaoxatridecamethylene)phthalocyaninato]digadolinium (ytterbium) which are characterized by MALDI-TOF mass spectrometry and UV-vis spectroscopy.