Linear and nonlinear optical Zn(II)-metal-organic materials. Correlation between molecular structure, crystal structure and chemical-physical properties

Table of content

Preface

Acknowledgements

About the contributors

Chapter 1 Metal–organics of ions with completed d[10] electronic configuration as NLO materials–general overview
1.1.Metal–organic complexes of carboxylates
1.2.Organic dyes as ligands in metal–organic NLO materials
1.3 N–aliphatic ligands in metal–organic NLO materials
1.4.N–heterocyclic ligands in metal–organic NLO materials
1.5.Ferrocene containing complexes as NLO materials
1.6.B–, S– and P– containing ligands in metal–organic NLO materials
1.7.Amino acids as homochiral ligands in metal–organic NLO materials
1.8.Polymer metal–organic materials
References

Chapter 2 Zinc tris (thiourea) sulphate and its derivatives as non-linear optical materials
2.1.Zinc tris (thiourea) sulphate as non–linear optical material
2.2.Metal–thiourea containing crystals as non–linear optical materials
References

Chapter 3 ZnII–containing metal–organic materials for linear and non–linear optical technologies
3.1.Metal–organic carboxylate complexes of ZnII–ion
3.2.ZnII–metal–organic complexes of N–heterocyclic ligands
3.3.ZnII–metal organics with aliphatic N–containing ligands
3.4.Porphyrin and phthalocyanine–based ZnII–metal–organic NLO materials
3.5.ZnII–complexes with organic dyes
3.6.B–, S– and P– containing ligands in metal–organic NLO materials
References

Chapter 4Quantum chemical treatment of linear and non–linear optical properties of metal–organics
4.1.Linear optical properties
4.1.1.Absorption spectra
4.1.1.1.Computation of the absorption energy
4.1.1.2.Computation of absorption band–shape
4.1.1.3.Computation of absorption intensity
4.1.2.Fluorescence spectra
4.1.2.1.Computation of emission energies
4.1.2.2.Computation of fluorescence band–shape
4.1.2.3.Computation of fluorescence intensity
4.2.Nonlinear optical properties
References

Appendix

Index

Preface

This book deals with chemistry and chemical–physical effects of ZnII–containing metal–organics with emergence as an interdisciplinary area of coordination chemistry, blending of electro optical and nonlinear optical materials research; optical fiber communication and optical computing technologies; data storage techniques; image processing; dynamic holography; printers; producing of harmonic generators; optical switching and limiting devices; fluorescence materials and more. In this context, the book collects new trends, and presents for first time more recent work in the field of applied oriented design of molecular scaffolds, synthesis, optical and nonlinear optical studies of coordination compounds of ZnII–ion. The book is divided into four chapters. The first Chapter 1 is designed to give readers a general overview on relevance of metal–organic materials containing metal ions with completed electronic d[10] configurations to mentioned above areas of applied sciences. We have chosen to introduce relationship between molecular structure and properties of zinc tris (thiourea) sulphate and its derivatives in a short Chapter 2, because of those compounds are seriously tested for an industrial scale application as NLO–phores. Chapter 3 is devoted, principally, to a correlation between molecular structure, crystal structure and chemical physical effects of ZnII–containing metal–organic materials, mainly part of our research work. Following this line, this book should therefore be seen as a high quality research literature source, highlighting new trends and prospectives in the field of optical and non-linear optical material technologies, based on coordination complexes of transition d[10] electronically configured metal ions, particularly reflecting in mind coordination compounds of ZnII–ion. We have considered certain sets of factors such as nature ZnII–ligand bond and photo-physical properties of ligands and their effect on electronic transitions of isolated molecules of coordination compounds and interacting ensembles in crystalline state. In this context we have provided a broad discussion on available experimental single crystal X–ray diffraction and mass spectrometric data of our metal–organic objects, their electronic absorption and fluorescence properties. A significant part is devoted to theoretical prediction of linear optical and non–linear optical properties of metal–organics as a useful approach in the design of new multifunctional materials. Chapter 4 concentrates on theoretical methodological formalism of most applicable quantum chemical methods, treating optical and non–linear optical phenomena, which are base on same thematic overall organization of this part of the book. The importance of this chapter is that it refers to basic computational chemistry methodology, associated with prediction of chemical–physical effects of metal–organics in gas– and condense phase, as a crucial step defining applied oriented chemical synthesis of new coordination compounds, thus producing results relevant to their real application as materials to optical and nonlinear optical technologies. The corresponding sections have a mixed reference–chapter and handbook style, addressing important questions to the context of Chapters 1–3, treating applied aspects of available theories; discussing the relationship between optical and non–linear optical properties of ZnII–complexes and their technological application. In this context, Chapter 4 can serve as methodological reference point. But the content of the book, generally, can be useful to scientific research of MSc and PhD students in “Chemistry”, which work involves fields such as coordination chemistry, applied materials research, crystal engineering, and the fourth.

Acknowledgments

The authors thank the Deutsche Forschungsgemeinschaft (DFG, Germany), supporting their study in this research topic within the frame of a project grant 255/22–1; the Alexander von Humboldt Stiftung (Germany) for instrumental equipment (single crystal X–ray diffractometer); and central instrumental laboratories for structural analysis at Dortmund University of Technology (Federal State Nordrhein–Westfalen, Germany) as well as analytical and computational laboratory clusters at the Institute of Environmental Research at the same University.

Conflicts of interest

Michael Spiteller has received research grant (255/22–1, DFG); Bojidarka Ivanova has received research grant (255/22–1, DFG).

Address correspondence to the authors:

Lehrstuhl für Analytische Chemie, Institut für Umweltforschung, Fakultät für Chemie und Chemische Biologie, Universität Dortmund, Otto–Hahn–Straße 6, 44221 Dortmund, Nordrhein–Westfalen, Deutschland;

E–Mails: B.Ivanova@web.de, B.Ivanova@infu.uni-dortmund.de (B.Ivanova);

E–Mail: M.Spiteller@infu.uni–dortmund.de (M.Spiteller).

About the contributors

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B. Ivanova has received MSc degree in “Chemical physics and theoretical chemistry” (1997) and PhD one in “Inorganic and analytical chemistry” (2001) at Sofia University “St. Kliment Ohridski” (Bulgaria). In 2006 she achieved a Habilitation of “Analytical chemistry” at the same Institution. Ivanova has been “associate professor” of analytical chemistry, and “Head of the group” of “Molecular Spectroscopy and Structural Analysis” (2006–2010). She occupied research position at the Institute of Environmental Research (INFU) of the Faculty of Chemistry and Chemical Biology at the Dortmund University of Technology (Germany) (2010–2011). At the same Institution she hold research positions under projects (2006,2010) sponsored by Deutscher Akademischer Austausch Dienst and Deutsche Forschungsgemeinschaft (Germany). She has been visiting researcher at Ruhr–University Bochum (Germany) under project initiatives sponsored by Alexander von Humboldt Stiftung (Germany) (2003,2007–2009). Ivanova is author and co-author of more than 220 scientific contributions, including books, textbooks and distance–learning e Textbooks, focusing her interest on molecular spectroscopy and structural analysis, inorganic and metal-organic chemistry of d – and f –elements, organometallic synthesis and catalysis. Ivanova has been awarded with Rectors’ Council award “Best young scientist" (Sofia University “St. Kliment Ohridski”, 2003) and “Pitagor Award” for “Best young scientist in whole area of sciences” of Bulgarian Ministry of Education (2009).

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Michael Spiteller finished his study (1976) and earned a doctoral degree (1979) in Chemistry at Georg–August University (Göttingen, Germany). Habilitation he achieved at Institute for Soil Science and Forest Hygiene (Göttingen) in 1985. After that, he lead “Research Group” at the Institute for Metabolism and Environmental Fate (Bayer Corp., Germany) for 8 years. He has appointed as professor “extraordinarius” at Georg–August University in 1990 and for “full” professor at University of Kassel (Germany). Now, Spiteller is professor and “Head” of the Institute of Environmental Research of the Faculty of Chemistry and Chemical Biology at the Dortmund University of Technology (Germany). In the same Institution, Spiteller holds “Research Group Leader Position” of “Environmental Analytical Chemistry” under the “focus” programme of Deutsche Forschungsgemeinschaft. He is member of numerous expert commissions at German Federal Offices and Councils. He serves also as member of editorial advisory boards of international specialized Journals such as “Fresenius Environmental Bulletin”, “Advances in Food Science”, “Pflanzenschutz Nachrichten” (Bayer), “Journal of Serbian Chemical Society” and the fourth. His work has led to over 500 scientific papers and presentations, review articles and monographs. He has been honoured member of Serbian Chemical Society and Institute of Organic Chemistry at the Bulgarian Academy of Sciences. He has been honoured with doctor title “honoris causa” from the University of Novi Sad (Serbia, 2006) and from the University of Sofia “St. Kliment Ohridski” (Bulgaria, 2009). Spiteller’s scientific interests encompass environmental analytical chemistry, mass spectrometric methodology and, natural products chemistry.

Keywords

ZnII –Coordination chemistry; Mass spectrometry; Quantum chemistry; Single crystal X–ray diffraction; Materials research; Optical properties; Nonlinear optics

Abbreviations and acronyms

ADF – Amsterdam density functional; ADC(2) – (Second–order) Algebraic diagrammatic construction; APCI – Atmospheric pressure chemical ionization (mass spectrometry); BDE – Bond dissociation energy; BO – Born–Oppenheimer (approximation); CC – Coupled cluster (approach); CCSD(T) – Coupled–cluster theory (higher–order); CDA – Charge decomposition analysis; CTTS – Charge–transfer–to–solvent bands; CID – Collision–induced dissociation; CIS – Single excitation configuration interaction; CN – Coordination number; DAST – 4–dimethylamino–N–methyl–4-stilbazolium tosylate; DFT – Density functional theory; DHM – Dichloromethalne; DMSO – Dimethylsulfoxide; DoS – Density of states; EAs – Electronic absorption (spectroscopy); EOM – Equations–of–motion; ECP(s) – Effective core potential(s); EFISH – Electric field induced second harmonic generation; EO – Electro–optical (coefficient, effect); ES – Excited state; ESI – Electrospray ionization (mass spectrometry); FC – Franck–Condon (approximation); Fs – Fluorescence (spectroscopy); FT – Fourier transform; GP – Gas–phase; GS – Ground state; HF – Hartree–Fock (method); HOMO – Highest occupied molecule orbital (H0); HRS – Hyper–Rayleigh scattering; IL – Intra–ligand; ISC – Inter–system crossing; JDoS – Joint density of state; L – Trp – Tryptophan; LANL2DZ – Los Alamos National Laboratory (doble–) pseudo-potentials; LLCT – Ligand–ligand charge transfer; LP – Liquid phase; LDoS – Local density of states (local radiative density of electromagnetic states); LR – Linear-response (formalism); LUMO – Lowest unoccupied molecule orbital (L0); M06–2X (and M06) – Meta–hybrid GGA DFT functional(s); MALDI – Matrix–assisted laser desorption ionization (mass spectrometry); MD – Molecular dynamics; MO – Molecular orbital; MCP – Model core potentials; MS – Mass spectrometry; NBO – Natural bond orbital (analysis); NEC – Natural electron configuration; NLO – Nonlinear optical (properties, effects); OL – Optical limiters; OPL – Optical power limiters (materials); OO–CIS – Orbital optimized CIS approach; PCM – Polarizable continuum model; PES(s) – Potential energy surface(s); rPBE – (revised) Perdew–Burke–Erzerhoff (theory); RPA – Random –Phase–Approximation; RSA – Reverse saturable absorption; SDD – Stuttgart–Dresden (pseudo–potentials); SOS – Scaled opposite–spin; SP – Solid phase; TDDFT – Time – dependent density functional theory; THF – Tetrahydrofuran; THG – Third harmonic generation; TPA – Two–photon absorption; UV – Ultraviolet (spectroscopy); VEE(s) – Vertical excitation energ(y)(ies); ZPVE – Zero–point vibrational energy; ZTS – Zinc tris (thiourea) sulphate.

Chapter 1 Metal–organics of ions with completed d[10] electronic configuration as NLO materials – general overview

SUMMARY

Much of the literature dealing with electro optical and nonlinear–optical technologies highlights the significant role of inorganic materials, having industrial scale application. The area of the coordination chemistry, particularly bearing in mind metal–organics of ions with configuration d[10] attracted much attention due to the fact that those compounds provide features with specific application to optical and NLO technologies, having significant advantages compared to many inorganic materials. Those molecular templates allow: (i) Structural functionalization of the molecular scaffold of the organic ligands, thus tuning easy their optical and NLO properties along with the coordination ability to the metal ion; (ii) Isolation of mixed–metallic and polynuclear compounds determining chemical–physical effects on the base on properties of the metal–centres along with those ones associated with the ligands, as mentioned in (i); (iii) Isolation of diversity of self–assembly structures of crystals of metal–organics; (iv) High optical and NLO efficiency; (v) Good–to–excellent crystal growth; (vi) High thermal stability without melting point processes; and more. All those factors and properties of metal–organics are discussed in this chapter in the light of the cumulated knowledge, organizing the content according to the type of the ligands.

INTRODUCTION

Considerable interest more recently has been focused on multi functional metal–organic materials, with tunable macroscopic functionality. Among advantages of those substances consist on combination of properties of individual components, meaning inorganic metal ion and corresponding organic ligands. Generally, the polar character of metal–to–ligand bond usually is characterized with large transition moment as well as a large exited state dipole moment, allowing to enhance hyperpolarizability (b) and in parallel second order nonlinear optical susceptibility c([2]) [1–24]. However, there are more then one major challenges in molecular design of new NLO materials based on metal–organic compounds [25]: (i) First of all, the efforts are concentrated on molecular design of organic ligand with preferably large hyperpolarizability (b). Typically there are involved conjugated push–pull D–p–A systems, like in design of purely organic NLO materials. Because of, in accordance with two level model, b depends on transition dipole moment and energy gap between a polar GS and separated first ES [25]; (ii) Determination of molecular structural factors governing optimal 1D–3D orientation of b–tensor components ensuring a maximal NLO response in corresponding bulk materials; (iii) Chemical synthesis of ligands; (iv) Second order NLO response depends not only on molecular hyperpolarizability, as written above, but of mutual disposition of molecules/ions in a bulk crystalline material. In this respect, a next factor in the design of new metal–organic NLO materials is (v) Different from “zero” macroscopic dipolar moment [4,5].

The isolation of non–centrosymmetric crystals is among the most problematic steps in the crystal engineering of metal–organics. Because of NLO–response, induced by charge displacement due to and effect of external field, can be occurred when hyperpolarizabilities such as mentioned above first hyperpolarizability as well as second (g) and more, as well as the higher order susceptibilities (c([2]), c([3]), and more) are greater than “zero” [26–30]. In this context only non–centrosymmetric crystals have b and c([2]) ¹ 0. The known strategies are associated with [6]: (i) Coordination between metal ion and a chiral ligand as counter ion; (ii) Coordination involving mixed ligands one of which is chiral agent; or (iii) Spontaneous crystallization, yielding to non–centrosymmetric crystals, using achiral ligands (Fig. 1.1) [13].

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Figure 1.1. Crystal structure of mono– and dinuclear CuII–trartarate mixed–ligand complex polymers {[Cu(1,10–phenanthroline) (H2tartrate) H2O].6H2O}n and {[Cu2 (1,10–phenanthroline)2 (tartrate)H2O].8H2O}n [13]

Towards point (i), broadly in the literature have been discussed metal complexes of homochiral agents, particularly, highlighting amino acids and their derivatives. Despite the fact that their crystallization yield to non–centrosymmetric crystals, those compounds often produce low quality single crystalline objects [31–34]. Our efforts in incorporation of chiral counter ion, using enantiomers of mandelic acid have resulted to series crystals, often yielding to a spontaneous crystallization of good quality single crystals, without additional efforts into improvement of crystal growth such as for example the shown in Figs. 1.2 and 1.3 pyridinium–4–aldoxime mandelate single crystal, crystallizing into a tetragonal non–centrosymmetric space group P43 or ephedrinium mandelate, crystallizing in non–centrosymmetric monoclinic C2 space group [32,36,36].

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Figure 1.2. Crystal structure of pyridinium–4–aldoxime mandelate (Space group P43) and photograph of a single crystal [35].

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Figure 1.3. Crystal structure of ephedrinium mandelate (Space group C2) and photograph of a single crystal [32]; Hs are omitted.

Regarding point (iii) of common strategies mentioned above, it is important to take into consideration that employment of non–chiral agents having, however, set of suitable functional groups allowing a formation of a large scale different intra/intermolecular interactions has resulted to isolation of non–centrosymmetric crystals as it is shown within the frame of numerouse objects discussed in this book. An example in this context is crystal structure of tyrammonium iodide [32], crystalizing into non–centrosymmetric P212121 space group (Fig. 1.4).

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Figure 1.4. Crystal structures of tyrammonium iodide (Space group P212121 [32])); Photographs of single crystals; Hs are omitted

1.1. Metal–organic complexes of carboxylates

Generally, the efforts over the years have shown that benzoic acid polyfunctional derivatives, particularly those themplates containing more than one –COOH structural fragment are particularly attrective scaffolds for design of metal–organic NLO materials with tunable linear optical and NLO properties due to their large ability to form diverce number of coordination modes to metal ions; large scale ionic stechiometry due to their polydeprotonating abilityp; along with great divercity of 0D–3D bonding network in crystalline state. Even simply substituted derivatives sich as X,Y–benzene dicarboxylic acids have remarkable ability to form mono– and polynuclear complexes, exhibityng following coordination fascion (Scheme 1.1) [37–45].

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Scheme 1.1. Coordination fashion of X,Y–benzene dicarboxylic acids [37–44]

The coordination ability of 1,2–benzenedicarboxylic acid (phthalic acid) to CdII–ion has shown formation of a mononuclear complex at molar ratio metal–to–ligand 1:4 (Fig.1.5) [42,43], where the ligand acts tetradentately. The corresponding polynuclear Zn4O(1,4-benzenedicarboxylate)3 single crystal, reported in [44] (Fig. 1.6), crystallizes in a cubic space group Abbildung in dieser Leseprobe nicht enthalten. ZnII–containing coordination mixed–ligand polymers with 5–nitroisophthalate [{Zn(5–nitroisophthalate)x(5–methoxyisophthalate)1-x(deuterated 4,4’–bipyridyl)}(DMF–MeOH)]n have been reported as well [45] (Fig. 1.7).

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Figure 1.5. Crystal structure of [Cd(phthalate)(H2O)]n coordination polymer [42,43]; Chemical diagram of the coordination fashion of the ligand.

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Figure 1.6. Crystal structure of Zn4O(1,4–benzenedicarboxylate)3 [44]; Hs are omitted.

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Figure 1.7. Crystal structure of [{Zn(5–nitroisophthalate)x(5–methoxyisophthalate)1-x(deuterated 4,4’–bipyridyl)}(DMF–MeOH)]n coordination polymer; Hs are omitted [45]

2,2’–Dihydroxy–[1,1’]binaphthalenyl–3,3’–dicarboxylic acid (Scheme A.1, Appendix) has been used as ligand for synthesis of series complexes with d[10] metal ions such as ZnII– (Chapter 3) or CgII–ions, respectively (Fig. 1.8) [46,47] The geometry of CdO6 chromophore is a distorted octahedron with r (Cd–O) bonds with bond lengths 2.405(4) and 2.420(3) Å, respectively. The free ligand exhibits an emission spectrum showing weak luminescence effect, by contrast to CdII–complex where intense green–blue emission at lmax = 523 nm occurs (lex = 355 nm). An assignment to this phenomenon is participation of CdII–ion in a chelating coordination mode, thus reducing the loss of energy via radiationless pathway. The MO computations have shown a LMCT effect via pL®5s transition. Other set of complexes of benzoic acid derivatives with metal ions, having electronic configuration d[10] have been reported, as well [48–53].

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Figure 1.8. Crystal structure of dinuclear CdII–complex [Cd2(L[1])2(H2O)6] of L[1] = 2,2’–Dihydroxy–[1,1’]binaphthalenyl–3,3’–dicarboxylic acid [47] (Hs are omitted)

X,Y,Z–benzenetricarboxylic acid derivatives have been used, designing metal–organics with d[10]–ions as well [54–57]. Some coordination modes to ZnII–, CdII– and AgI–metal ions are shown in Scheme 1.2. The coordination polymer [{Ag(1,3,5–benzenetricarboxylate)2}{Ag2(1,3,5–benzenetricarboxylate)}]n [55] exhibits unsupported Ag–Ag interactions with r (Ag–Ag) distances Î 2.9626(12)–3.2782(8) Å, which are shorter, comparing to those ones for van der Waals contacts (r (Ag–Ag), 3.40 Å) (Fig. 1.9).

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Scheme 1.2. Coordination fashion of X,Y,Z–benzene tricarboxylic acids to ZnII–, CdII– and AgI–metal ions [54–57]

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Figure 1.9. Crystal structure of [{Ag(1,3,5–benzenetricarboxylate)2}{Ag2(1,3,5–benzenetricarboxylate)}]n coordination polymer [55]

Benzene–1,2,3,4–tetracarboxylic acid (L[1]) has been used as template of polydentate ligand, isolating series mixed ligand complexes of AgI–ion with 4,4’–bipyridine as a second ligand (L[2]) [48]. Four type coordination polymers have been investigated by single crystal X–ray diffraction, determining chemical compositions: [Ag4L[1]]n, {[Ag2.5(L[1]) (L2)2] [AgL[2]]. [AgL[2](H2O)] (NO3)0.5 (H2O)9}n, {[Ag2.5(L[1]) (L[2])2] [AgL[2]]. [AgL[2](H2O)] (NO3)0.5(H2O)9}n, {[Ag5(L[1])2 (L[2])4] [AgL[2]]. [AgL[2](H2O)]2(H2O)16}n, and {[Ag2(L[1])(H2O)[AgL[2]]2}n, respectively. The first and the last complex crystallizes in non–centrosymmetric space groups Pac21 and I212121, respectively (Fig. 1.10). The L[1] exhibit complex multidentate character, allowing formation of diverse number of polynuclear complexes, which makes this ligand excellent template for field of crystal engineering of new metal–organic NLO–phores (Scheme 1.3).

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Figure 1.10. Crystal structure of non–centrosymmetric coordination polymers [Ag4L[1]]n and {[Ag2(L[1]) (H2O)[AgL[2]]2}n [48].

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Scheme 1.3. Chemical diagrams and coordination fashion of benzene–1,2,3,4– and benzene–1,2,3,5–tetracarboxylic acids [48,58]

Fs data of free benzene–1,2,3,4–tetracarboxylic acid have shown a band at lmax = 370 nm upon lex = 280 nm due to p®p* and n®p* IL transitions. While the corresponding AgI–complexes have shown lmax = 546 and 553 nm upon laser irradiation lex = 388 and 319 nm. The observed red–shifting of lmax in the coordination compounds have been associated with MLCT. Generally, the AgI–complexes have a low intensive emission due to spin–orbital coupling of AgI–ion with electronic configuration d[10] [48]. SHG measurements have shown intensity about 0.4 and 0.6 over urea. Biphenyl–2,2′,6,6′–tetracarboxylic acid has been used for design of CdII–based NLO materials in [49]. The isolated complex crystallizes in non–centrosymmetric cubic I-43d space system and group, showing SHG intensity 0.8 times than KDP crystal used as a standard. A –COOH substituted diphenyl–diazene has bee used a a template for design of NLO materials, too [50]. R substituted R–isophthalic acids, where R = H, OH or t –But substituents have been employed as ligands studying the coordination ability of d[10] ions as an effort to obtain bimetallic polynuclear coordination compounds [51]. Along with benzene–1,2,3,4–tetracarboxylic acid reported in [48], as particularly promising template of poly-functional benzoic acid containing ligand series ZnII–, CdII– and CoII– complexes with 4–hydroxy–iosphthalic acid in the presence of N–heterocyclic mixed ligand of 2,2’–bipyridine have been isolated and elucidated structurally and spectroscopically [52,53]. Comparing with the coordination ability of benzene–1,2,3,4–tetracarboxylic acid, 4–hydroxy–iosphthalic acid has shown series binding modes to metal centres as depicted in Scheme 1.4. Both trinuclear CoII– and ZnII– complexes crystallise in non–centrosymmetric space system P21, thus showing SHG intensities about 0.5 and 0.02 than urea.

The 1,4–benzenedicarboxylate, 1,3–benzenedicarboxylate, and 5–hydroxy–1,3–benzenedicarboxylate molecular scaffolds have been employed as ligand templates in the design of bimetallic metal–organic NLO materials in [59].

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Scheme 1.4. Coordination fashion of 4–hydroxy–iosphthalic acid; M = ZnII–, CdII– and CoII–ions [52]

1,2,3,4,5–Benzenepentacarboxylic acid has demonstrated a great ability to form diverse coordination architectures with various metal ions. Particularly the interaction with ZnII–ion has shown set of bonding fashions (Scheme 1.5). There are isolated a series of mixed ligand 1D and 2D complexes [Zn6(m3–OH)2(benzenepentacarboxylate ion)2(H2O)6]n, [Zn5(m3–OH)2(benzenepentacarboxylate ion)2(2,2’–bipyridyl)2]n, [Zn2(benzenepentacarboxylate ion)(1,10–phenanthroline)2(H2O)2]n, and [Zn5(benzenepentacarboxylate ion)2(1,10–phenanthroline)4(H2O)3]n.2nH2O [60] (Fig. 1.11). A Zn6(m3–OH)2 hexanuclear cluster has been identified in the same work.

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Scheme 1.5. Coordination fashion of 1,2,3,4,5–benzenepentacarboxylic acid [60]

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Figure 1.11. Crystal structure of ZnII–complex of 1,2,3,4,5–benzenepentacarboxylic acid [60]

1.2. Organic dyes as ligands in metal–organic NLO materials

In accordance with strategic point (i) (Section 1.1, Chapter 1), considerable efforts have been focused on coordination compounds or complex salts with organic dyes as ligand components/counter ions [4,25,61–63]. The developments in this direction serve both materials research on new NLO materials based on organic NLO–phores as well as metal–organic and hybrid functional materials. One of the most well developed organic NLO material is trans –4′– (dimethylamino)– N –methyl–4–stilbazolium tosylate (L[1],L[2]), which has been used in design of metal–organic ZnII–containing mixed and in parallel mixed–ligand metallic materials yielding to complex salt {[L[1]]4[M2Zn(C2O4)6].[L[2]]2.2H2O} [25]. Series dye–derivatives along with AgI–complexes with Schiff’s bases have been reported [61,63] (Scheme 1.6). As far as a significant part of studied organic dyes containing N–heterocyclic structural fragment, usually involve in inner coordination sphere of metal chromophore, those type of dyes are discussed in Sections 3.2 or 3.4. (Chapter 3). The advantages of organic dye as molecular templates for design of new NLO and Fs materials are their tunable, and in parallel large molecular hyperpolarizability due to strong electron donating and accepting groups connected via a conjugated p–system, thus governing ILCT excitations. The Schiff’ bases of type L[2]–L[12] and stilbazolium salts of L[1] type shown in [63] (Schemes 1.6 and A.8, Appendix) have stabilized, depending on the type of the substituents a quinolide like form determining a batochromic effect of 120 nm. It depends on solvent polarity. Particularly, from the illustrated few examples such as form is typical for L[5] and L[9] as well as the like (See Scheme A.8, Appendix). To Schiff’s class of dyes we have added the Michler’s ketone derivatives as well as, isolated in course of our work in this topic (Table 1.1, Scheme 1.6). Some of last compounds are also prominent templates for ligands to ions with completed electronic configuration d[10]. Due to multidentate character of those ligands their protonation/deprotonation behavior has been studied using quantum chemical methods in [61,63]. The dipole moments and NLO properties are summarized in Table 1.1 [61]. The EAs and Fs characteristics are shown in Fig. 1.12 and Table 1.1. The coordination behavior and effect of bonding to ZnII– and AgI–metal ions on linear–optical and NLO properties of the shown classes of dyes (L[1]–L[12]) have been studied theoretically as a part of a molecular design of new metal–organic NLO–phores [61–63]. Detail comparative analysis between theoretical and experimental solid–state and solution spectra can be found in the cited references [61,63] as well as a short discussion is carried out in Chapter 3. Herein, we have shown the effect of protonation on NLO properties, involving polyprotonated forms as well as (Table 1.2), comparing with data about cationic DAST residue, showing following values at the same theoretical level: mtot = 9.8132 D; atot = –47.83 and btot = 403.85; (atot and btot values are computed, using equations (3.4) and (3.6), Chapter 3, Section 3.4) . As it is shown the polyprotonated forms have btot values over neutral ones, thus justifying a design of crystalline organic and metal–organic salts of ionic species. Comparing with DAST cationic residue, Schiff’s bases, have larger btot values, where in the case of diprotonated 3–amino–7–[(4-pyrrolidin–1–yl–benzylidene)–amino]–5–(4-pyrrolidin–1–yl–phenyl)–5,8–dihydro–[1,2,4] triazolo [4,3–a] pyrimidine–6–carbonitrile btot value (btot = 2015.86) is 5 times over DAST’s cation one as shown above [61].

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Scheme 1.6. Chemical diagrams of substituted organic dyes [61–63]; Photographs of the crystals; Coordination positions to Michler’s ketone derivatives

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Figure 1.12. EAs of Schiff’s dyes, their neutral and protonated forms [61–63]; Energy transitions; Orbital contribution; MOs

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Table 1.1. Dipole moment (mtot [D]), polarizability (aij [D–Å]) and hyperpolarizability (bijk [D–Å[2]], gijkl [D–Å[3]]) tensor components of Schiff’s dye–ligands [61]

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Table 1.2. EAs data of functionalized organic dyes shown in Scheme 1.6 (TDDFT, RPA, CIS) [61,63]; E – Energy

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