SYNTHESIS AND CHARACTERIZATION OF NEW ORGANIC MOLECULES AND INORGANIC-ORGANIC HYBRID MATERIALS WITH INTERESTING LINEAR AND SECOND ORDER NON LINEAR OPTICAL PROPERTIES
Creators: name: TORDIN, ELISA
Publisher: name: Universit� degli Studi di Milano
Year: 2010

description: The different stages of technological evolution are characterized in terms of the dominant type of tools used in each of them. We passed through the `stone age', the `copper age' and the `iron age' and now we are probably in the `electron age'. After having done a wonderful job, today it looks as if electronic technologies have started experiencing their limits. For example, today's `information explosion' and communication problems demand very large bandwidths without cross talk, larger than that electronics can provide. What could be the technology that can tackle the growing needs of tomorrow?
Photonics is being studied today as a possible alternate technology for the future. Investigations are on to harness the capability of the photon to carry information and energy. Fortunately, success has already been achieved in the area of communications. Optical fibers, not copper cables, are already being used to carry huge amounts of information across the great oceans. However, among the three ?C?s (communication, computing and control), communication is the only one that is currently implying photonic devices. Photonic switches and optical computers are still in the laboratories and not yet in the marketplace. The major bottleneck in this area is not in solving technological problems or in perfecting theoretical understanding, but in developing suitable materials. 
In this field, materials with non linear optical (NLO) properties seem to be extremely appealing in fact NLO effects allow the manipulation of laser light beams, extending the frequency range provided by normal laser sources into the ultraviolet and infrared regions, and may thus form the basis of all-optical computing devices.
In order to be implied in a device, the NLO materials must satisfy some requirement such as good NLO properties, high laser damage threshold, fast optical response time, wide phase matchable angle, architectural flexibility for molecular design and morphology, ability to process into crystals and thin films, optical transparency (no absorption at fundamental and SH wavelengths), synthetically facile, environmental friendly and high mechanical strength and thermal stability.
During this three-year research the attention was to the synthesis and the investigation of the second harmonic NLO properties of new organic and inorganic-organic hybrid material.
NLO characterization has been performed in solution using the EFISH technique, the Kurtz-Perry method has been implied for the measurements in the solid state while the Maker?s fringe technique has been use for measurements on film.
In the field of inorganic-organic hybrid materials, the synthesis of new members of the family of compounds with general formula [DAMS]4[MIII2MII(C2O4)6]2?DAMBA?2H2O (where MIII = Rh, Fe, Cr; MII = Co, Ni, DAMS = trans-4-(4-dimethylaminostyryl)-1-methylpyridinium; DAMBA = para-dimethylamino benzaldeide) has been prepared and, in particular, the derivatives containing CoII and NiII have been isolated by slight modification of the synthesis reported by Cariati et al. for the MnII and ZnII derivatives. The SHG of these new materials is extremely high, of the same order on magnitude of DAST (trans-4-(4-dimethylaminostyryl)-1-methylpyridinium p-toluensulfonate) and it is related to the organization into J aggregates of the [DAMS+] chromophores. These materials are not only interesting for their SHG but also for the tuning of their magnetic properties by varying the MII/MIII couple.
During the optimization of the synthesis of these compounds, a phase containing only [DAMS]I and DAMBA has been isolated. The [DAMS+] chromophores are organized in colums in a configuration typical of J aggregates and the presence of the templating agent DAMBA induces the arrangement of the colums in a fish-bone-like architecture. The SHG of this new compound is, once again, related to the presence on J aggregates.
The tendency to form J aggregates of [DAMS+] chromophores has also been exploited in the preparation of film of DAST in poly(methyl methacrylate (PMMA) with high, stable and long-lasting SHG using the Poling technique. The in situ growth of homogeneously dispersed oriented nanocrystals with sizes of less than 100 nm has been observed in PMMA films with 4 wt% of the ionic second order NLO chromophore DAST obtained by spincoating of CHCl3?CH3OH (2/1) solutions. This is achieved by a two step process: corona poling at 8 kV and 90�C followed, in the absence of electric field, by controlled thermal annealing up to 140�C. 
The investigation of the NLO properties has also been extended to chromophores in solution and the molecular hyperpolarizability has been determinate by EFISH technique. Of particular interest is the compound 8-N,N-dibutylamino-2-azachrysene which is characterized by a large hyperpolarizability value and very high thermal stability, properties that make it good candidate as building block for NLO active materials.
Particular interest has been given to solid state luminescent materials for their growing interest both from a scientific and a technological point of view. Aggregation caused quenching (ACQ) processes however represent an obstacle to the development of most luminogens in the condensed phase. This is why particularly fascinating are those materials showing higher emission intensity in the solid state than in solution. In this filed, the emissive properties of the molecule 4-dimethylamino-2-benzylidene malonic acid dimethyl ester, a very simple push-pull molecule have been investigated. It is weakly emissive in solution and in the amorphous phase but becomes highly emissive in the crystalline phase according to what has been indicated as Crystallization Induced Emission (CIE). Thanks to combined emission, 1H and 13C NMR spectroscopies, it has been demonstrated that a restricted intramolecular rotation (RIR) phenomen is at the origin of this behavior. Moreover this molecule possesses interesting acidochromic properties opening to sensor and optoelectronic applications. 
During a 7 months research period spent at UCSB (University of California, Santa Barbara) in Prof. Ford?s laboratories, the synthesis and characterization of Cu(I) complexes with a photolabile CS2 moiety have been studied. In particular, two new complexes have been obtained: [Cu(dmp)(PPh3)(tBuOOC-CS2)] (dmp = 2,9-dimethyl-1,10- phenanthroline, tBuOOC-CS2 = O-t-butyl-1,1- dithiooxalate ester ) is a rare example of tetracoordinated CuI complex with three different ligands while [Cu(tBuOOC-CS3)(Br)][PPh3Bz] is an air stable threecoordinated CuI complex. Further study has to be performed in order to determine whether or not CS2 is photogenerated upon irradiation with visible light.